Tin sulfide is being widely investigated as an earth-abundant light harvesting material, but recorded efficiencies for SnS fall far below theoretical limits. We describe the synthesis and characterization of the single-crystal tin sulfides (SnS, SnS2, and Sn2S3) through chemical vapor transport, and combine electronic structure calculations with time-resolved microwave conductivity measurements to shed light on the underlying electrical properties of each material. We show that the coexistence of the Sn(II) and Sn(IV) oxidation states would limit the performance of SnS in photovoltaic devices due to the valence band alignment of the respective phases and the “asymmetry” in the underlying point defect behavior. Furthermore, our results suggest that Sn2S3, in addition to SnS, is a candidate material for low-cost thin-film solar cells

Previous investigations of the field‐effect mobility in poly(3‐hexylthiophene) (P3HT) layers revealed a strong dependence on molecular weight (MW), which was shown to be closely related to layer morphology. Here, charge carrier mobilities of two P3HT MW fractions (medium‐MW: Mn = 7 200 g mol−1; high‐MW: Mn = 27 000 g mol−1) are probed as a function of temperature at a local and a macroscopic length scale, using pulse‐radiolysis time‐resolved microwave conductivity (PR‐TRMC) and organic field‐effect transistor measurements, respectively. In contrast to the macroscopic transport properties, the local intra‐grain mobility depends only weakly on MW (being in the order of 10−2 cm2 V−1 s−1) and being thermally activated below the melting temperature for both fractions. The striking differences of charge transport at both length scales are related to the heterogeneity of the layer morphology. The quantitative analysis of temperature‐dependent UV/Vis absorption spectra according to a model of F. C. Spano reveals that a substantial amount of disordered material is present in these P3HT layers. Moreover, the analysis predicts that aggregates in medium‐MW P3HT undergo a “pre‐melting” significantly below the actual melting temperature. The results suggest that macroscopic charge transport in samples of short‐chain P3HT is strongly inhibited by the presence of disordered domains, while in high‐MW P3HT the low‐mobility disordered zones are bridged via inter‐crystalline molecular connections.

IntroductionSolar cells employing metal halide perovskites as light absorbers have undergone a tremendous development over the past years, resulting in photovoltaic devices with record efficiencies exceeding 22%. [1][2][3] The impressive progress in device efficiency is mainly due to (i) optimizing experimental procedures to obtain perovskite materials with improved crystallinity, (ii) adjusting the perovskite composition, and (iii) investigating different transport materials. However, it remains a major Perovskite-based photovoltaics have been rapidly developed, with record power conversion efficiencies now exceeding 22%. In order to rationally design efficient and stable perovskite solar cells, it is important to understand not only charge trapping and recombination events, but also processes occurring at the perovskite/transport material (TM) interface, such as charge transfer and interfacial recombination. In this work, time-resolved microwave conductivity measurements are performed to investigate these interfacial processes for methylammonium lead iodide and various state-of-the-art organic TMs. A global kinetic model is developed, which accurately describes both the dynamics of excess charges in the perovskite layer and transfer to chargespecific TMs. The authors conclude that for state-of-the-art materials, such as Spiro-OMeTAD and PCBM, the charge extraction efficiency is not significantly affected by intra-band gap traps for trap densities under 10 15 cm -3 . Finally, the transfer rates to C60, PCBM, EDOT-OMeTPA, and Spiro-OMeTAD are sufficient to outcompete second order recombination under excitation densities representative for illumination by AM1.5.

A 1,3,5-benzenetrisamide with three pending hexaalkoxytriphenylene groups has been synthesized as an example of an interesting class of intermolecular H-bond-stabilized columnar discotic liquid crystalline materials. The material forms a plastic hexagonal discotic phase that does not crystallize on cooling from the isotropic phase, even after annealing for a few days at room temperature. X-ray and computational studies provide a detailed model for the organization of this material. The charge carrier mobility, 0.12 cm2 V-1 s-1 at 180 °C, is the highest ever reported for liquid crystalline triphenylene systems, and even increases with temperature. The factors responsible for this behavior are discussed.

Highly photoconductive films of CdSe nanocrystals have been prepared by exchanging the original bulky ligands with 1,2-ethanedithiol (EDT) and 1,2-ethanediamine (EDA). Different methods to achieve this exchange, layer-by-layer (LbL) deposition and soaking of drop-casted films, have been compared in detail. Introduction of EDT and EDA by the soaking method results in a broadening of the optical absorption due to disorder in the film. In contrast, the width of the absorption features is unaffected in the LbL films, while the position of the first optical absorption peak is red-shifted by tens of millielectronvolts. The photoluminescence is completely quenched for the LbL films. These findings are characteristic for strong and homogeneous electronic coupling between the quantum dots (QDs) in the LbL films. The photoconductivity of these films was studied with the time-resolved microwave conductivity (TRMC) technique. With this electrodeless technique effects of electrode injection on charge transport are avoided, so that information about the intrinsic mobility of charge carriers is obtained. We find that in simple drop-casted films the conductivity is mainly imaginary and dominated by the polarizability of photogenerated excitons. When the orginal ligands are exchanged by soaking or by the LbL procedure, the conductivity becomes real and dominated by interparticle transport of free charge carriers. It is found that the product of the exciton dissociation yield and the charge carrier mobility is 4 × 10 -3 cm 2 /(V s) in the LbL grown films with EDA capping molecules. This implies that a surprisingly high fraction of free carriers is generated or, alternatively, that the carrier mobility is higher than all previously reported mobility values for layers of CdSe QDs.