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@article{nokey,

title = {Near-Infrared Emitting Lanthanide Catecholate Giant Single Crystals - Morphology Control and Photon Down-Conversion},

author = {M I Sch\"{o}nherr and A Biewald and A M\"{a}hringer and T J Koller and P Mayer and M D\"{o}blinger and A Hartschuh and D D Medina},

url = {\<Go to ISI\>://WOS:001535016700001},

doi = {10.1002/adfm.202507464},

issn = {1616-301X},

year  = {2025},

date = {2025-07-25},

journal = {Advanced Functional Materials},

abstract = {Lanthanide coordination polymers (Ln-CPs), an intriguing type of near-infrared (NIR) emitting materials, hold significant potential as fast-response platforms in light-emitting devices. The controlled crystallization of a series of Ln-DHBQ (2,5-dihydroxy-1,4-benzoquinone) CPs yielding photoactive single crystals is reported herein. Single crystal X-ray diffraction analysis revealed the impact of the synthesis conditions employed on the structure of Ln-DHBQ CPs. Hereby, the well-known isostructural series of [Ln2(C6H2O4)3(H2O)6]18H2O (Ln = Yb (1), Nd (3)) is expanded with a novel member [Ln2(C6H2O4)3(H2O)4]6H2O (Ln = Yb (2)), that crystallizes in the monoclinic space group C2/m instead of the trigonal space group R 3$bar 3$, which is typical of the parent series. Scanning electron microscopy and optical microscopy images showed that controlover the size and morphology of Yb-DHBQ and Nd-DHBQ crystals was achieved, where emerging as either disc-like single crystals of up to 100 mu m in size or faceted large single crystals up to 500 mu m, respectively. This series of Ln-DHBQ (1-3) features NIR photoluminescence with nanosecond lifetimes. Photon bunching is observed on the timescale of the excited-state lifetime in the second-order time correlation function, demonstrating a photon down-conversion process for both Yb-DHBQ CPs. This places Ln-DHBQ crystals as excellent candidates for the development of operational platforms requiring intense and short period light emission read out cycles.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Atomic-layer assembly of ultrathin optical cavities in van der Waals heterostructure metasurfaces},

author = {L Sortino and J Biechteler and L Lafeta and L K\"{u}hner and A Hartschuh and L D Menezes and S A Maier and A Tittl},

url = {\<Go to ISI\>://WOS:001495232400001},

doi = {10.1038/s41566-025-01675-4},

issn = {1749-4885},

year  = {2025},

date = {2025-05-26},

journal = {Nature Photonics},

abstract = {Photonics has been revolutionized by advances in optical metasurfaces, unlocking design and engineering opportunities for flat optical components. Similarly, layered two-dimensional materials have enabled breakthroughs in physics via the deterministic assembly of vertical heterostructures, allowing precise control over the atomic composition of each layer. However, integrating these fields into a single system has remained challenging, limiting progress in atomic-scale optical cavities and metamaterials. Here we demonstrate the concept of van der Waals heterostructure metasurfaces, where ultrathin multilayer van der Waals material stacks are shaped into precisely engineered resonant nanostructures for enhancing light-matter interactions. By leveraging quasi-bound states in the continuum physics, we create intrinsic high-quality-factor resonances originating from WS2 monolayers encapsulated in hexagonal boron nitride at thicknesses below 130 nm, achieving room-temperature strong coupling and polaritonic photoluminescence emission. Furthermore, the metasurface-coupled exciton-polaritons exhibit strong nonlinearities, leading to a saturation of the strong-coupling regime at ultralow fluences of \<1 nJ cm(-2), three orders of magnitude lower than in previous two-dimensional-material-based cavity systems. Our approach monolithically integrates metasurfaces and van der Waals materials and can be extended to the vast library of existing two-dimensional materials, unlocking new avenues for ambient operation of ultrathin polaritonic devices with atomic-scale precision and control.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Designing Atomically Precise and Robust COF Hybrids for Efficient Photocatalytic CO₂ Reduction},

author = {L Spies and M E G Carmo and M D\"{o}blinger and Z Xu and T Xue and A Hartschuh and T Bein and J Schneider and A O T Patrocinio},

url = {https://doi.org/10.1002/smll.202500550},

doi = {https://doi.org/10.1002/smll.202500550},

issn = {1613-6810},

year  = {2025},

date = {2025-03-03},

journal = {Small},

volume = {n/a},

number = {n/a},

pages = {2500550},

abstract = {Abstract Hybrid photocatalysts based on molecular species and solid substrates are elegant solutions for improving the performance and stability of molecular catalytic systems aiming at solar-driven CO2 conversion. In this work, a new dibenzochrysene-based covalent organic framework (COF) is developed to accept ReI centers, keeping its high crystallinity and allowing for atomistic control of the position of the catalytic centers. The rigid structure of the COF leads to long-term stability under illumination, whereas the efficient light-harvesting capability and the strong electronic interactions between the COF and the ReI centers lead to CO evolution rates of up to 1.16 mmol g?1 h?1. The favorable photocatalytic performance of this novel ReI-COF offers new insights regarding the development of efficient photocatalytic hybrid systems.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Printed CsMg\textendashZnO ETLs achieve over 9 % efficiency in PbS quantum dot solar cells},

author = {R Holfeuer and C Maheu and H Illner and R Hoojier and H Balakrishnan and B M\"{a}rz and S Lotfi and H Sezen and K M\"{u}ller-Caspary and T Bein and J P Hofmann and T Ameri and A Hartschuh and A Yousefiamin},

url = {https://www.sciencedirect.com/science/article/pii/S2468606925000218},

doi = {https://doi.org/10.1016/j.mtener.2025.101813},

issn = {2468-6069},

year  = {2025},

date = {2025-03-01},

journal = {Materials Today Energy},

volume = {48},

pages = {101813},

abstract = {Zinc oxide (ZnO) is a key electron transport layer (ETL) material in next-generation lead sulfide (PbS) colloidal quantum dot solar cells (CQDSCs) due to its high transparency, strong exciton binding energy, and good electron mobility. Here, we demonstrate a scalable doctor-blading printing protocol for ZnO ETLs that integrates dual defect passivation with magnesium (Mg2⁺) and caesium (Cs⁺) and employs solvent engineering to achieve uniform, defect-minimized films. Using a ternary solvent blend (methanol, chloroform, and 2-methoxyethanol) optimizes the ink's viscosity and boiling point, preventing particle migration and ensuring full substrate coverage. Our modified ZnO ink leads to improved crystallinity, smoother surfaces, and reduced trap states, boosting the fill factor (FF) and short-circuit current (Jsc). Consequently, we achieve a power conversion efficiency increase from 5.98 % to 9.53 % using a printed CsMg-ZnO film. Notably, 80 % of dual-doped devices exceeded 7.5 % efficiency, demonstrating high reproducibility and reliability. This performance enhancement underscores the effectiveness of dual metal ion treatment and solvent engineering strategies in overcoming printability challenges. Moreover, the compatibility of our approach with low-temperature processing and established coating techniques paves the way for seamless integration into large-scale manufacturing, bringing PbS CQDSCs closer to commercial viability.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {The Role of Fluorine-Functionalized Organic Spacers for Defect Passivation and Low-Dimensional Phase Formation in 3D MAPI Perovskite Solar Cells},

author = {A Semerci and J Urieta-Mora and S Driessen and A Buyruk and R Hooijer and A Molina-Ontoria and B Alkan and S Akin and M Fanetti and H Balakrishnan and A Hartschuh and S Tao and N Mart\'{i}n and P M\"{u}ller-Buschbaum and S Emin and T Ameri},

url = {https://doi.org/10.1002/adfm.202423109},

doi = {https://doi.org/10.1002/adfm.202423109},

issn = {1616-301X},

year  = {2025},

date = {2025-02-14},

journal = {Advanced Functional Materials},

volume = {n/a},

number = {n/a},

pages = {2423109},

abstract = {Abstract Widespread application of organic-inorganic halide perovskites (OIHP) still faces a major obstacle in mitigating moisture-induced degradation. Integrating organic spacers, as defect passivation facilitators along with low-dimensional phase (LDP) formation is an effective approach to enhance the efficiency and robustness of 3D methyl ammonium lead iodide (MAPI) in photovoltaics (PV). Here, the formamidinium cation (FA+) employing 3,5-difluorobenzene-1-carboximidamidium iodide (2F), 4-(trifluoromethyl)benzene-1-carboximidamidium iodide (3F), and 2,3,4,5,6-pentafluorobenzene-1-carboximidamidium iodide (5F) organic spacers as passivation layer in 3D/LDP OIHP solar cells is utilized. Fluorine atom position and quantity in organic spacers change the optoelectronic characteristics of the perovskites, enhancing hydrophobicity, facilitating LDP formation, and augmenting dipole moments, thereby facilitating charge separation processes. PV performance analysis reveals that 3F-treated 3D/LDP devices achieve the highest efficiency of 19.22%. Experimental results and density functional theory (DFT) studies attribute the higher performance of 3F-modified devices to effective LDP formation, enhanced passivation of defect states at perovskite surfaces and grain boundaries, the highest dipole moment and lowest band gap among the evaluated spacers. The stability tests show that, after 1000 h, 3F- and 5F-modified 3D/LDP OIHP devices retain over 85% of their initial efficiency. This research opens novel avenues for designing appropriate organic spacers to attenuate defects in 3D/LDP PV devices.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Crystalline porous frameworks based on double extension of metal\textendashorganic and covalent organic linkages},

author = {K Endo and S Canossa and F Heck and D M Proserpio and M S Istek and F Stemmler and J Van Slageren and S Hartmann and A Hartschuh and B V Lotsch},

url = {https://doi.org/10.1038/s44160-024-00719-x},

doi = {10.1038/s44160-024-00719-x},

issn = {2731-0582},

year  = {2025},

date = {2025-01-14},

journal = {Nature Synthesis},

abstract = {Reticular chemistry is a powerful strategy to design materials with fine-tuned chemical functionality and porosity, such as metal\textendashorganic frameworks (MOFs) and covalent organic frameworks (COFs). MOFs typically show high crystallinity due to their reversible coordinative bonds, and the organic backbone of COFs provides chemical stability. Here we synthesize metal\textendashorganic\textendashcovalent\textendashorganic frameworks (MOCOFs) that combine both crystallinity and stability in a single framework by the double extension of metal\textendashorganic and covalent organic linkages. Several MOCOFs are obtained by reaction between a cobalt aminoporphyrin and dialdehydes, which are interconnected by cobalt\textendashamine coordination and imine condensation to form three-dimensional networks. The MOCOFs exhibit chiral topological nets, large surface areas, high crystallinities and high chemical stabilities due to the two types of extended linkages. Thus, MOCOFs present a reticular design strategy that further diversifies the chemical and structural space of porous solids.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Spatiotemporal Spectroscopy of Fast Excited-State Diffusion in 2D Covalent Organic Framework Thin Films},

author = {L Spies and A Biewald and L Fuchs and K Merkel and M Righetto and Z Xu and R Guntermann and R Hooijer and L M Herz and F Ortmann and J Schneider and T Bein and A Hartschuh},

url = {https://doi.org/10.1021/jacs.4c13129},

doi = {10.1021/jacs.4c13129},

issn = {0002-7863},

year  = {2025},

date = {2025-01-02},

journal = {Journal of the American Chemical Society},

abstract = {Covalent organic frameworks (COFs), crystalline and porous conjugated structures, are of great interest for sustainable energy applications. Organic building blocks in COFs with suitable electronic properties can feature strong optical absorption, whereas the extended crystalline network can establish a band structure enabling long-range coherent transport. This peculiar combination of both molecular and solid-state materials properties makes COFs an interesting platform to study and ultimately utilize photoexcited charge carrier diffusion. Herein, we investigated the charge carrier diffusion in a two-dimensional COF thin film generated through condensation of the building blocks benzodithiophene-dialdehyde (BDT) and N,N,N′,N′-tetra(4-aminophenyl)benzene-1,4-diamine (W). We visualized the spatiotemporal evolution of photogenerated excited states in the 2D WBDT COF thin film using remote-detected time-resolved PL measurements (RDTR PL). Combined with optical pump terahertz probe (OPTP) studies, we identified two diffusive species dominating the process at different time scales. Initially, short-lived free charge carriers diffuse almost temperature-independently before relaxing into bound states at a rate of 0.7 ps\textendash1. Supported by theoretical simulations, these long-lived bound states were identified as excitons. We directly accessed the lateral exciton diffusion within the oriented and crystalline film, revealing remarkably high diffusion coefficients of up to 4 cm2 s\textendash1 (200 K) and diffusion lengths of several hundreds of nanometers and across grain boundaries. Temperature-dependent exciton transport analysis showed contributions from both incoherent hopping and coherent band-like transport. In the transport model developed based on these findings, we discuss the complex impact of order and disorder on charge carrier diffusion within the WBDT COF thin film.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Probing Noncentrosymmetric 2D Materials by Fourier Space Second Harmonic Imaging},

author = {L Lafeta and S Hartmann and B Rosa and S Reitzenstein and L M Malard and A Hartschuh},

url = {https://doi.org/10.1021/acsphotonics.4c01724},

doi = {10.1021/acsphotonics.4c01724},

year  = {2025},

date = {2025-01-01},

journal = {ACS Photonics},

abstract = {Second-harmonic generation (SHG) has been established as a powerful tool for probing noncentrosymmetric materials. In the typical implementation, the SHG intensity is detected while rotating the polarization of the incident laser field and of the second harmonic relative to the sample. Although effective, this approach can be time-consuming and laborious. Here, we present a novel experimental approach for directly determining the symmetry and crystal orientation of noncentrosymmetric 2D materials. This approach involves capturing SH images generated by tightly focused laser beams in Fourier space and exploits the material’s symmetry and SHG’s coherent nature. For a Gaussian laser beam, the crystal orientation of the 2D material can be derived from the ellipticity of the observed SHG patterns, whereas for an azimuthally polarized laser beam, the detected SHG pattern directly reveals the crystal lattice together with its orientation. A microscopic model that treats SHG as a coherent superposition of fields radiated by dipolar emitters within the laser-illuminated area and that considers the symmetry of the χ(2)-tensor quantitatively describes the detected patterns. The approach presented provides a fast and precise tool for determining crystal symmetry and orientation and will be applicable to materials with broken inversion symmetry.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Overcoming Intrinsic Quantum Confinement and Ultrafast Self-Trapping in Ag\textendashBi\textendashI- and Cu\textendashBi\textendashI-Based 2D Double Perovskites through Electroactive Cations},

author = {R Hooijer and S Wang and A Biewald and C Eckel and M Righetto and M Chen and Z Xu and D Bl\"{a}tte and D Han and H Ebert and L M Herz and R T Weitz and A Hartschuh and T Bein},

url = {https://doi.org/10.1021/jacs.4c04616},

doi = {10.1021/jacs.4c04616},

issn = {0002-7863},

year  = {2024},

date = {2024-10-02},

journal = {Journal of the American Chemical Society},

volume = {146},

number = {39},

pages = {26694-26706},

abstract = {The possibility to combine organic semiconducting materials with inorganic halide perovskites opens exciting pathways toward tuning optoelectronic properties. Exploring stable and nontoxic, double perovskites as a host for electroactive organic cations to form two-dimensional (2D) hybrid materials is an emerging opportunity to create both functional and lead-free materials for optoelectronic applications. By introducing naphthalene and pyrene moieties into Ag\textendashBi\textendashI and Cu\textendashBi\textendashI double perovskite lattices, intrinsic electronic challenges of double perovskites are addressed and the electronic anisotropy of 2D perovskites can be modulated. (POE)4AgBiI8 containing pyrene moieties in the 2D layers was selected from a total of eight new 2D double perovskites, exhibiting a favorable electronic band structure with a type IIb multiple quantum well system based on a layer architecture suitable for out-of-plane conductivity and leading to a photocurrent response ratio of almost 3 orders of magnitude under AM1.5G illumination. Finally, an exclusively parallelly oriented thin film of (POE)4AgBiI8 was integrated into a device to construct the first pure n = 1 Ruddlesden\textendashPopper 2D double perovskite solar cell.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Interpenetrated Donor\textendashAcceptor Heterojunctions in 2D Conjugated Dibenzo[g,p]chrysene-Based Kagome Covalent Organic Frameworks},

author = {T Xue and R Guntermann and A Biewald and D Bl\"{a}tte and D D Medina and A Hartschuh and T Bein},

url = {https://doi.org/10.1021/acsami.4c09286},

doi = {10.1021/acsami.4c09286},

issn = {1944-8244},

year  = {2024},

date = {2024-09-11},

journal = {ACS Applied Materials \& Interfaces},

volume = {16},

number = {36},

pages = {48085-48093},

abstract = {Dibenzo[g,p]chrysene can be viewed as a constrained propeller-shaped tetraphenylethylene with reduced curvature and has been utilized to construct dual-pore kagome covalent organic frameworks (COFs) with tightly packed two-dimensional (2D) layers owing to its rigid and more planar structural characteristics. Here, we introduce 2D COFs based on the node 4,4′,4″,4‴-(dibenzo[g,p]chrysene-2,7,10,15-tetraphenyl)tetraamine (DBCTPTA) featuring extended conjugation compared to the dibenzo[g,p]chrysene-3,6,11,14-tetraamine (DBCTA) node. We establish two exceptionally crystalline imine-linked 2D COFs with a hexagonal dual-pore kagome structure based on the DBCTPTA core. The newly synthesized thienothiophene (TT) and benzodithiophene (BDT)-based DBCTPTA COFs show a tight stacking behavior between adjacent layers. Furthermore, we obtained an unprecedented, interpenetrated electron-donor/acceptor host\textendashguest system with an electron-donating BDT DBCTPTA COF synthesized in situ with the soluble fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) serving as molecular acceptor. The BDT DBCTPTA COF@PCBM film shows a much shorter amplitude-averaged PL lifetime of 7 ± 2 ps compared to 30 ± 4 ps of the BDT DBCTPTA COF film, indicating the light-induced charge transfer process. The successful in situ formation of interpenetrated donor\textendashacceptor heterojunctions within 2D COFs offers a promising strategy for establishing D\textendashA heterojunctions in diverse framework materials with open channel systems.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Ultrafast Phase-Control of the Nonlinear Optical Response of 2D Semiconductors},

author = {L Lange and K Wang and S Bange and L Lafeta and B Rosa and S Reitzenstein and J M Lupton and A Hartschuh},

url = {https://doi.org/10.1021/acsphotonics.4c00388},

doi = {10.1021/acsphotonics.4c00388},

year  = {2024},

date = {2024-08-21},

journal = {ACS Photonics},

volume = {11},

number = {8},

pages = {3112-3122},

abstract = {Nonlinear optical phenomena, such as sum-frequency generation (SFG) and four-wave mixing (FWM), play a central role in various applications ranging from spectroscopy, laser pulse characterization, and design to all-optical switching. Monolayer semiconducting transition metal dichalcogenides (TMDs) feature particularly strong nonlinear light-matter interactions which result from the large oscillator strength of tightly bound excitons. Here, we tune the spectral phase of a broadband 12 fs laser pulse resonant with the first excitonic transition in monolayer WSe2 and MoSe2 to coherently control the nonlinear signal intensities via the phase of the interacting optical fields. We find that stretching the laser pulse compared to the transform-limited case allows for an enhancement of FWM intensities by a factor of ∼2. For low excitation densities the corresponding optimal spectral phase profile can be predicted by a classical model based on the measured linear absorption spectrum of the TMD monolayer without free parameters. For increasing excitation densities, however, the influence of excitonic resonances vanishes. Excitation-induced dephasing of the resonance together with the onset of the Mott transition at high excitation densities inhibit coherent population control at room temperature. In contrast to FWM, SFG cannot be enhanced by phase-shaping as compared to the transform-limited pulse. Instead, SFG appears to be unaffected by the first excitonic resonance, which we attribute to the dominating role of higher-energy bands in this process.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Van der Waals heterostructure metasurfaces: atomic-layer assembly of ultrathin optical cavities},

author = {L Sortino and J Biechteler and L Lafeta and L K\"{u}hner and A Hartschuh and L D S Menezes and S A Maier and A Tittl},

year  = {2024},

date = {2024-07-23},

journal = {arXiv preprint arXiv:2407.16480},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Regioisomerism in Thienothiophene-Based Covalent Organic Frameworks─A Tool for Band-Gap Engineering},

author = {R Guntermann and L Frey and A Biewald and A Hartschuh and T Clark and T Bein and D D Medina},

url = {https://doi.org/10.1021/jacs.4c02365},

doi = {10.1021/jacs.4c02365},

issn = {0002-7863},

year  = {2024},

date = {2024-06-12},

journal = {Journal of the American Chemical Society},

volume = {146},

number = {23},

pages = {15869-15878},

abstract = {The craft of tuning optical properties is well-established for crystalline inorganic and hybrid solids. However, a far greater challenge is to tune the optical properties of organic materials systematically by design. We now introduce a synthesis concept that enables us to alter the optical properties of crystalline covalent organic frameworks (COFs) systematically using isomeric structures of thienothiophene-based building blocks (T23/32T) combined with a variety of tetratopic aromatic amines, e.g., the Wurster moiety (W\textendashNH2). This concept is demonstrated for the synthesis of COFs in bulk and film forms and provides highly crystalline and porous isomeric COFs featuring predesigned photophysical properties. The band gap of the framework can be tuned continuously and precisely by chemically doping the pristine W23TT COF with its related constitutional isomer building block. Density-functional theory investigations of COF model compounds indicate that the extent of π-conjugation is among the key characteristics enabling the band-gap engineering.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Wavelength-tunable ultrafast two arm fiber laser system for transient interferometric scattering microscopy on nanoscopic objects},

author = {K Birkmeier and A Hartschuh},

url = {https://opg.optica.org/josab/abstract.cfm?URI=josab-41-2-493},

doi = {10.1364/JOSAB.510611},

year  = {2024},

date = {2024-02-01},

journal = {Journal of the Optical Society of America B},

volume = {41},

number = {2},

pages = {493-499},

abstract = {Ultrafast time-resolved microscopy of single nano-objects is particularly challenging because of minute sample volumes and correspondingly small signal levels together with the possibility of photobleaching. We present a compact pulsed two arm fiber laser-based system suited for highly sensitive transient interferometric scattering (TiSCAT) microscopy of nanomaterials. A continuously tunable probe arm is used for spectrally resolved detection of the transient sample response in the range between 810 and 960\ nm upon pulsed excitation at 780\ nm by the pump arm. Coupled to a scanning confocal microscope with high numerical aperture objective, the system provides spectral maps with sub-300\ nm spatial and 300\ fs temporal resolution. We tested the platform using monolayer M o S e 2 and individual (6,4) single-walled carbon nanotubes as model samples. Confocal microscopy images recorded for an exfoliated monolayer M o S e 2 reveal spatially varying excited state decay, highlighting the need for local probing. Spectrally resolved TiSCAT measurements on individual (6,4) single-walled carbon nanotubes show that the transient response is dominated by ground-state bleaching with picosecond recovery times. The obtained data illustrate the excellent noise properties and stability of the newly developed laser system, which allow for nearly shot-noise limited TiSCAT detection at the low probe fluences required for avoiding photodegradation of sensitive nanomaterials.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Cu/Ag\textendashSb\textendashI Rudorffite Thin Films for Photovoltaic Applications},

author = {R Hooijer and A Weis and W Kaiser and A Biewald and P D\"{o}rflinger and C Maheu and O Arsatiants and D Helminger and V Dyakonov and A Hartschuh and E Mosconi and F De Angelis and T Bein},

url = {https://doi.org/10.1021/acs.chemmater.3c01837},

doi = {10.1021/acs.chemmater.3c01837},

issn = {0897-4756},

year  = {2023},

date = {2023-11-16},

journal = {Chemistry of Materials},

volume = {35},

number = {23},

pages = {9988-10000},

abstract = {In the search for lead-free perovskites, silver pnictohalides recently gained attention as novel perovskite-inspired materials for photovoltaics due to their high stability, low toxicity, and promising early efficiencies, especially for indoor applications. Recent research on such “rudorffites” mainly addresses silver bismuth iodides (Ag\textendashBi\textendashI), while their antimony analogues are hardly investigated due to intrinsic challenges in the synthesis of Sb-based thin films. Here, we establish a synthetic route to prepare Ag\textendashSb\textendashI thin films by employing thiourea as a Lewis-base additive. Thin film morphologies were further optimized by alloying them with Cu, resulting in solar cells with an improved power conversion efficiency of 0.7% by reducing undesired side phases. Density functional theory calculations and optical characterization methods support the incorporation of Cu into a Cu1\textendashxAgxSbI4 phase, keeping the overall stoichiometry and band gap virtually unchanged upon alloying. Our results further reveal the detrimental role of Ag point defects representing trap states in the band gap, being responsible for low open-circuit voltages and subgap absorption and emission features. Moreover, additional minor amounts of Bi are shown to boost the efficiency and stabilize the performance over a wider compositional range. Despite the remaining challenges regarding device performance, we demonstrate a strong increase in external quantum efficiency when reducing the light intensity, highlighting the potential of Ag\textendashSb\textendashI rudorffites for indoor photovoltaics.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Photoexcitation Control of Excitation Relaxation in Mixed-Phase Ruddlesden-Popper Hybrid Organic-Inorganic Lead-Iodide Perovskites},

author = {A Stadlbauer and L Eyre and A Biewald and F Rauh and M W Heindl and S Liu and J Zerhoch and S Feldmann and A Hartschuh and F Deschler},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adom.202301331},

doi = {https://doi.org/10.1002/adom.202301331},

issn = {2195-1071},

year  = {2023},

date = {2023-10-02},

journal = {Advanced Optical Materials},

volume = {n/a},

number = {n/a},

pages = {2301331},

abstract = {Abstract The electronic states and exciton binding energies of layered Ruddlesden-Popper (RP) metal-halide perovskites can be tailored through changes of their chemical composition, yielding multi-phase systems with complex energy cascades. Ultrafast photoexcitation relaxation with transfer dynamics into domains of increasing layer number has been reported for these materials. Here, ultrafast optical spectroscopy is used to report an unexpected excitation energy dependence of photoexcitation relaxation dynamics in mixed-dimensional benzylammonium cesium lead iodide RP perovskite (BeA2CsPb2I7) thin films, which gives rise to spectrally broadband luminescence over the visible region. Using transient absorption and photoluminescence spectroscopy it is found that excitations, which are formed in the n = 2 RP-phase after photoexcitation with ≈0.2 electron volt excess energy, transfer to higher layer number RP-phases on unexpectedly slow timescales of tens of picoseconds. Further, it is observed that such excitations are initially optically passive. Notably, luminescence occurs under these conditions from multiple RP-phases with optical bandgaps across the visible range, yielding broadband luminescence. The results hold potential for realization of broadband white-light emitters and other light-emitting devices.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Layer-By-Layer Printed Metal Hybrid (Cs:FA)PbI3 Perovskite Nanocrystal Solar Cells},

author = {M A Reus and A Krifa and Q A Akkerman and A Biewald and Z Xu and D P Kosbahn and C L Weindl and J Feldmann and A Hartschuh and P M\"{u}ller-Buschbaum},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adom.202301008},

doi = {https://doi.org/10.1002/adom.202301008},

issn = {2195-1071},

year  = {2023},

date = {2023-09-01},

journal = {Advanced Optical Materials},

volume = {n/a},

number = {n/a},

pages = {2301008},

abstract = {Abstract Mixed halide perovskite nanocrystals in the form of cesium/formamidinium lead triiodide ((Cs:FA)PbI3) offer great potential for efficient and stable solar cells. To date, large-scale production with roll-to-roll compatible deposition methods remains difficult and requires detailed research on each involved processing step. Here, a proof-of-concept study about slot-die coating (printing) the active layer of (Cs:FA)PbI3-based nanocrystal solar cells is presented. Structural and morphological changes during ligand exchange of long-chain oleic acid and oleylamine by Pb(NO3)2, and top-layer FAI passivation are investigated. Ligand exchange improves the processability of the nanocrystal layer and enhances charge transport. It also changes texture from face-on toward edge-on orientation as grazing-incidence X-ray scattering studies indicate. Ligand exchange and FAI passivation redshift photoluminescence and prolong charge carrier lifetime in the printed nanocrystal films. The proof-of-concept feasibility of printing metal halide perovskite nanocrystal films for solar cells is shown by building 20 devices with a median power conversion efficiency of 6.39%.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Room-temperature synthesis of lead-free copper(I)-antimony(III)-based double perovskite nanocrystals},

author = {S Wang and D Han and C Maheu and Z Xu and A Biewald and H Illner and R Hooijer and T Mayer and A Hartschuh and H Ebert and T Bein},

url = {https://aip.scitation.org/doi/abs/10.1063/5.0144708},

doi = {10.1063/5.0144708},

year  = {2023},

date = {2023-04-05},

journal = {APL Materials},

volume = {11},

number = {4},

pages = {041110},

abstract = {In the field of perovskite solar cells, explorations of new lead-free all-inorganic perovskite materials are of great interest to address the instability and toxicity issues of lead-based hybrid perovskites. Recently, copper-antimony-based double perovskite materials have been reported with ideal band gaps, which possess great potential as absorbers for photovoltaic applications. Here, we synthesize Cs2CuSbCl6 double perovskite nanocrystals (DPNCs) at ambient conditions by a facile and fast synthesis method, namely, a modified ligand-assisted reprecipitation method. We choose methanol as a solvent for precursor salts as it is less toxic and easily removed in contrast to widely used dimethylformamide. Our computational structure search shows that the Cs2CuSbCl6 structure containing alternating [CuCl6]5− and [SbCl6]3− octahedral units is a metastable phase that is 30 meV/atom higher in energy compared to the ground state structure with [CuCl3]2− and [SbCl6]3− polyhedra. However, this metastable Cs2CuSbCl6 double perovskite structure can be stabilized through solution-based nanocrystal synthesis. Using an anion-exchange method, Cs2CuSbBr6 DPNCs are obtained for the first time, featuring a narrow bandgap of 0.9 eV. Finally, taking advantage of the solution processability of DPNCs, smooth and dense Cs2CuSbCl6 and Cs2CuSbBr6 DPNC films are successfully fabricated.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Ultrafast hot electron\textendashhole plasma photoluminescence in two-dimensional semiconductors},

author = {F B Sousa and R Perea-Causin and S Hartmann and L Lafet\'{a} and B Rosa and S Brem and C Palekar and S Reitzenstein and A Hartschuh and E Malic and L M Malard},

url = {http://dx.doi.org/10.1039/D2NR06732C},

doi = {10.1039/D2NR06732C},

issn = {2040-3364},

year  = {2023},

date = {2023-03-13},

journal = {Nanoscale},

volume = {15},

number = {15},

pages = {7154-7163},

abstract = {The transition metal dichalcogenide family of semiconducting two-dimensional materials has recently shown a prominent potential to be an ideal platform to study the exciton Mott transition into electron\textendashhole plasma and liquid phases due to their strong Coulomb interactions. Here, we show that pulsed laser excitation at high pump fluences can induce this exciton Mott transition to an electron\textendashhole plasma in mono and few-layer transition metal dichalcogenides at room temperature. The formation of an electron\textendashhole plasma leads to a broadband light emission spanning from the near infrared to the visible region. In agreement with our theoretical calculations, the photoluminescence emission at high energies displays an exponential decay that directly reflects the electronic temperature \textendash a characteristic fingerprint of unbound electron\textendashhole pair recombination. Furthermore, two-pulse excitation correlation measurements were performed to study the dynamics of electronic cooling, which shows two decay time components, one of less than 100 fs and a slower component of few ps associated with the electron\textendashphonon and phonon\textendashlattice bath thermalizations, respectively. Our work may shed light on further studies of the exciton Mott transition into other two-dimensional materials and their heterostructures and its applications in nanolasers and other optoelectronic devices.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Probing the ultrafast dynamics of excitons in single semiconducting carbon nanotubes},

author = {K Birkmeier and T Hertel and A Hartschuh},

url = {https://doi.org/10.1038/s41467-022-33941-2},

doi = {10.1038/s41467-022-33941-2},

issn = {2041-1723},

year  = {2022},

date = {2022-10-21},

journal = {Nature Communications},

volume = {13},

number = {1},

pages = {6290},

abstract = {Excitonic states govern the optical spectra of low-dimensional semiconductor nanomaterials and their dynamics are key for a wide range of applications, such as in solar energy harvesting and lighting. Semiconducting single-walled carbon nanotubes emerged as particularly rich model systems for one-dimensional nanomaterials and as such have been investigated intensively in the past. The exciton decay dynamics in nanotubes has been studied mainly by transient absorption and time-resolved photoluminescence spectroscopy. Since different transitions are monitored with these two techniques, developing a comprehensive model to reconcile different data sets, however, turned out to be a challenge and remarkably, a uniform description seems to remain elusive. In this work, we investigate the exciton decay dynamics in single carbon nanotubes using transient interferometric scattering and time-resolved photoluminescence microscopy with few-exciton detection sensitivity and formulate a unified microscopic model by combining unimolecular exciton decay and ultrafast exciton-exciton annihilation on a time-scale down to 200 fs.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Phase-Selective Four-Wave Mixing of Resonant Plasmonic Nanoantennas},

author = {V Giegold and K Ko\la̧Taj and T Liedl and A Hartschuh},

url = {https://doi.org/10.1021/acsphotonics.2c01362},

doi = {10.1021/acsphotonics.2c01362},

year  = {2022},

date = {2022-10-11},

journal = {ACS Photonics},

abstract = {Metallic nanoantennas are key components of a wide range of optical techniques that exploit their plasmonic response for signal amplification and extremely sensitive detection. For nonlinear techniques, the higher-order plasmonic response of a nanoantenna can be predicted by the product of the nanoantenna’s linear susceptibilities, known as Miller’s rule, provided that the spatial field distributions at the fundamental and the nonlinear frequencies are the same. Here, we show that Miller’s rule also holds for ultra-broadband excitation pulses and that it can be utilized to predict the frequency dependence of the near-degenerate four-wave mixing (ND-FWM) intensities generated by individual resonant plasmonic nanoantennas. Importantly, this implies that the nanoantenna’s nonlinear response can be deterministically controlled and further optimized by varying the spectral phase of the laser pulse. We demonstrate this by measuring the chirp dependence of the ND-FWM signal and observe an enhancement of up to 60% depending on the position of the plasmon resonance with respect to the laser spectrum, in agreement with model predictions. Finally, we exploit this phase control for chirp-selective confocal imaging of resonant nanoantennas. Our findings may help improve the sensitivity of nonlinear techniques such as plasmon-enhanced coherent anti-Stokes Raman scattering.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Silver-Bismuth Based 2D Double Perovskites (4FPEA)4AgBiX8 (X = Cl, Br, I): Highly Oriented Thin Films with Large Domain Sizes and Ultrafast Charge-Carrier Localization},

author = {R Hooijer and A Weis and A Biewald and M T Sirtl and J Malburg and R Holfeuer and S Thamm and A Y Amin and M Righetto and A Hartschuh and L M Herz and T Bein},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adom.202200354},

doi = {https://doi.org/10.1002/adom.202200354},

issn = {2195-1071},

year  = {2022},

date = {2022-07-03},

urldate = {2022-07-03},

journal = {Advanced Optical Materials},

volume = {10},

issue = {14},

pages = {2200354},

abstract = {Abstract Two-dimensional (2D) hybrid double perovskites are a promising emerging class of materials featuring superior intrinsic and extrinsic stability over their 3D parent structures, while enabling additional structural diversity and tunability. Here, we expand the Ag\textendashBi-based double perovskite system, comparing structures obtained with the halides chloride, bromide, and iodide and the organic spacer cation 4-fluorophenethylammonium (4FPEA) to form the n = 1 Ruddlesden\textendashPopper (RP) phases (4FPEA)4AgBiX8 (X = Cl, Br, I). We demonstrate access to the iodide RP-phase through a simple organic spacer, analyze the different properties as a result of halide substitution and incorporate the materials into photodetectors. Highly oriented thin films with very large domain sizes are fabricated and investigated with grazing incidence wide angle X-ray scattering, revealing a strong dependence of morphology on substrate choice and synthesis parameters. First-principles calculations confirm a direct band gap and show type Ib and IIb band alignment between organic and inorganic quantum wells. Optical characterization, temperature-dependent photoluminescence, and optical-pump terahertz-probe spectroscopy give insights into the absorption and emissive behavior of the materials as well as their charge-carrier dynamics. Overall, we further elucidate the possible reasons for the electronic and emissive properties of these intriguing materials, dominated by phonon-coupled and defect-mediated polaronic states.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Helical Anthracene\textendashEthyne-Based MOF-74 Analogue},

author = {P I Scheurle and A M\"{a}hringer and T Haug and A Biewald and D Axthammer and A Hartschuh and L Harms and G Wittstock and D D Medina and T Bein},

url = {https://doi.org/10.1021/acs.cgd.1c01145},

doi = {10.1021/acs.cgd.1c01145},

issn = {1528-7483},

year  = {2022},

date = {2022-05-04},

journal = {Crystal Growth \& Design},

volume = {22},

number = {5},

pages = {2849-2853},

abstract = {A flexible, electron-rich building block was integrated into the backbone of a metal\textendashorganic framework with a MOF-74 topology. The building block comprises a central anthracene core connected to acetylene groups. Solvothermal synthesis with Mn2+ yields a highly crystalline anthracene\textendashethyne-based MOF-74 structure. It shows an unusual helical rod-like morphology, exhibiting visible light absorption and photoluminescence.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {A novel electrically conductive perylene diimide-based MOF-74 series featuring luminescence and redox activity},

author = {P I Scheurle and A Biewald and A M\"{a}hringer and A Hartschuh and D D Medina and T Bein},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/sstr.202100195},

doi = {https://doi.org/10.1002/sstr.202100195},

issn = {2688-4062},

year  = {2022},

date = {2022-01-11},

journal = {Small Structures},

volume = {n/a},

number = {n/a},

abstract = {Metal-organic frameworks (MOFs) featuring significant electrical conductivity constitute a growing class of materials, with intriguing possible applications as porous semiconductors or supercapacitors. If such features are combined with photoluminescence, additional functionalities such as selective chemical sensing become accessible. Here, we incorporate perylene diimide (PDI) based linear building blocks into the MOF-74 topology with the three metal ions Zn2+, Mg2+ and Ni2+, resulting in a new series of MOFs, namely PDI-MOF-74(M). PDI derivatives are dye molecules exhibiting remarkable optical properties, high electron mobilities, as well as interesting redox behavior. However, PDI-based 3D MOFs are very rare and to date were only reported once. The frameworks of the PDI-MOF-74(M) series exhibit high crystallinity, electrical conductivity and show well-defined redox activity. In addition, the frameworks of the series feature photoluminescence in the orange and red spectral regions. With this work we expand the series of electroactive MOF-74 structures as well as the group of 3D PDI-based MOFs, hence opening up the development of novel MOFs with promising optoelectronic properties comprising PDI building blocks. This article is protected by copyright. All rights reserved.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {MOF-74(M) Films Obtained through Vapor-Assisted Conversion\textemdashImpact on Crystal Orientation and Optical Properties},

author = {P I Scheurle and A M\"{a}hringer and A Biewald and A Hartschuh and T Bein and D D Medina},

url = {https://doi.org/10.1021/acs.chemmater.1c00743},

doi = {10.1021/acs.chemmater.1c00743},

issn = {0897-4756},

year  = {2021},

date = {2021-07-28},

journal = {Chemistry of Materials},

volume = {33},

number = {15},

pages = {5896-5904},

abstract = {In recent years, metal\textendashorganic frameworks (MOFs) with the structure MOF-74 have attracted much interest owing to their tunable pore aperture, high surface area, and electrical conductivity. The synthesis of well-defined, highly crystalline thin films of MOF-74 is of paramount importance for their implementation into device-based applications such as in chemical sensing, optoelectronics, gas storage, and separations. Here, we present the synthesis of highly crystalline MOF-74 (M = Zn2+, Mg2+, Ni2+, and Co2+) films by vapor-assisted conversion. MOF-74(M) thin films were grown on bare glass, quartz, gold, and silicon surfaces, showing high crystallinity, crystal orientation, and average thicknesses of 500 nm. By including a benzoic acid modulator, oriented MOF-74(Zn) films, with the crystallographic c-axis of the MOF crystallites oriented horizontally to the surface, were obtained on all substrates. In addition, highly crystalline MOF-74(Mg) was grown on glass and gold substrates with the crystallographic c-axis aligned orthogonally to the surface. Moreover, randomly oriented highly crystalline MOF-74(Co) and MOF-74(Ni) films were synthesized on glass, quartz, gold, and silicon. The pore accessibility of the obtained films was examined by means of krypton sorption measurements, revealing permanent and accessible porosity, reaching a BET surface area of 975 cm2/cm2 for MOF-74(Mg). Steady-state and time-resolved photoluminescence studies show emission in the blue spectral region of MOF-74(Zn and Mg) on quartz with a biexponential decay. In addition, confocal photoluminescence mapping confirmed a homogeneous MOF film surface with a similar emission profile over the whole examined area of 70 μm × 70 μm.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {1,10-Phenanthroline as an Efficient Bifunctional Passivating Agent for MAPbI3 Perovskite Solar Cells},

author = {A Buyruk and D Bl\"{a}tte and M G\"{u}nther and M A Scheel and N F Hartmann and M D\"{o}blinger and A Weis and A Hartschuh and P M\"{u}ller-Buschbaum and T Bein and T Ameri},

url = {https://doi.org/10.1021/acsami.1c05055},

doi = {10.1021/acsami.1c05055},

issn = {1944-8244},

year  = {2021},

date = {2021-07-09},

urldate = {2021-07-09},

journal = {ACS Applied Materials \& Interfaces},

abstract = {Passivation is one of the most promising concepts to heal defects created at the surface and grain boundaries of polycrystalline perovskite thin films, which significantly deteriorate the photovoltaic performance and stability of corresponding devices. Here, 1,10-phenanthroline, known as a bidentate chelating ligand, is implemented between the methylammonium lead iodide (MAPbI3) film and the hole-transport layer for both passivating the lead-based surface defects (undercoordinated lead ions) and converting the excess/unreacted lead iodide (PbI2) buried at interfaces, which is problematic for the long-term stability, into “neutralized” and beneficial species (PbI2(1,10-phen)x},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Tailored Local Bandgap Modulation as a Strategy to Maximize Luminescence Yields in Mixed-Halide Perovskites},

author = {S Feldmann and T Neumann and R Ciesielski and R H Friend and A Hartschuh and F Deschler},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adom.202100635},

doi = {https://doi.org/10.1002/adom.202100635},

issn = {2195-1071},

year  = {2021},

date = {2021-06-12},

journal = {Advanced Optical Materials},

volume = {n/a},

number = {n/a},

pages = {2100635},

abstract = {Abstract Halide perovskites have emerged as high-performance semiconductors for efficient optoelectronic devices, not least because of their bandgap tunability using mixtures of different halide ions. Here, temperature-dependent photoluminescence microscopy with computational modelling is combined to quantify the impact of local bandgap variations from disordered halide distributions on the global photoluminescence yield in mixed-halide perovskite films. It is found that fabrication temperature, surface energy, and charge recombination constants are keys for describing local bandgap variations and charge carrier funneling processes that control the photoluminescence quantum efficiency. It is reported that further luminescence efficiency gains are possible through tailored bandgap modulation, even for materials that have already demonstrated high luminescence yields. The work provides a novel strategy and fabrication guidelines for further improvement of halide perovskite performance in light-emitting and photovoltaic applications.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Local Disorder at the Phase Transition Interrupts Ambipolar Charge Carrier Transport in Large Crystal Methylammonium Lead Iodide Thin Films},

author = {A Biewald and N Giesbrecht and T Bein and P Docampo and A Hartschuh and R Ciesielski},

url = {https://doi.org/10.1021/acs.jpcc.0c06240},

doi = {10.1021/acs.jpcc.0c06240},

issn = {1932-7447},

year  = {2020},

date = {2020-08-25},

journal = {The Journal of Physical Chemistry C},

volume = {124},

number = {38},

pages = {20757-20764},

abstract = {The low-temperature transition from a tetragonal to an orthorhombic crystal phase in methylammonium lead iodide (MAPI) is accompanied by drastic changes in the charge carrier mobility around a critical temperature of approximately 164 K. This transition is studied here using photoluminescence (PL) microscopy on large crystal MAPI thin films, which is extremely sensitive to modifications of the charge carrier dynamics and can resolve physical properties on a single-grain level. The key observation is that ambipolar charge carrier diffusion suddenly stops when the temperature falls below the phase transition temperature. From coexisting PL bands and their spatial distribution, it is concluded that the temperature range from just below the phase transition until about 150 K is determined by a mixed phase where small orthorhombic and tetragonal domains coexist. This results in local disorder, which hinders ambipolar charge carrier diffusion.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Non-linear Raman scattering intensities in graphene},

author = {V Giegold and L Lange and R Ciesielski and A Hartschuh},

url = {http://dx.doi.org/10.1039/C9NR10654E},

doi = {10.1039/C9NR10654E},

issn = {2040-3364},

year  = {2020},

date = {2020-02-18},

journal = {Nanoscale},

abstract = {We show that the Raman scattering signals of the two dominant Raman bands G and 2D of graphene sensitively depend on the laser intensity in opposite ways. High electronic temperatures reached for pulsed laser excitation lead to an asymmetric Fermi\textendashDirac distribution at the different optically resonant states contributing to Raman scattering. This results in a partial Pauli blocking of destructively interfering quantum pathways for G band scattering, which is observed as a super-linear increase of the G band intensity with laser power. The 2D band, on the other hand, exhibits sub-linear intensity scaling due to the blocking of constructively interfering contributions. The opposite intensity dependencies of the two bands are found to reduce the observed 2D/G ratio, a key quantity used for characterizing graphene samples, by more than factor two for electronic temperatures around 3000 K.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Temperature-Dependent Ambipolar Charge Carrier Mobility in Large-Crystal Hybrid Halide Perovskite Thin Films},

author = {A Biewald and N Giesbrecht and T Bein and P Docampo and A Hartschuh and R Ciesielski},

url = {https://doi.org/10.1021/acsami.9b04592},

doi = {10.1021/acsami.9b04592},

issn = {1944-8244},

year  = {2019},

date = {2019-06-12},

journal = {ACS Applied Materials \& Interfaces},

volume = {11},

number = {23},

pages = {20838-20844},

abstract = {Perovskite-based thin-film solar cells today reach power conversion efficiencies of more than 22%. Methylammonium lead iodide (MAPI) is prototypical for this material class of hybrid halide perovskite semiconductors and at the focal point of interest for a growing community in research and engineering. Here, a detailed understanding of the charge carrier transport and its limitations by underlying scattering mechanisms is of great interest to the material’s optimization and development. In this article, we present an all-optical study of the charge carrier diffusion properties in large-crystal MAPI thin films in the tetragonal crystal phase from 170 K to room temperature. We probe the local material properties of individual crystal grains within a MAPI thin film and find a steady decrease of the charge carrier diffusion constant with increasing temperature. From the resulting charge carrier mobility, we find a power law dependence of μ ∝ Tm with m = −(1.8 ± 0.1). We further study the temperature-dependent mobility of the orthorhombic crystal phase from 50 to 140 K and observe a distinctly different exponent of m = −(1.2 ± 0.1).},

keywords = {},

pubstate = {published},

tppubtype = {article}

}