Chalcohalide semiconductors are an emergent class of materials for optoelectronics. Here, the first work on BiSI chalcohalide thin film photodetectors (PDs) is presented. An entirely new method for the fabrication of bismuth chalcohalide thin films (BiOI and BiSI) is developed. This method circumvents the use of any ligands or counter ions during fabrication and provides highly pure thin films free of carbon residues and other contaminants. When integrated into lithographically patterned lateral PDs these BiSI thin films show outstanding performances and high stability. The direct ≈1.55 eV bandgap of BiSI perfectly accommodates optical sensing over the full visible spectrum. The responsivity (R) of the BiSI PDs reaches 62.1 A W−1, which is the best value reported to date across chalcohalide materials of any type. The BiSI PDs display remarkable sensitivity to low light levels, supporting a broad operational detectivity ≈1012 Jones over four decades in light intensity, with a peak specific detectivity (D*) of 2.01 × 1013 Jones. The dynamics of photocurrent generation are demonstrated to be dominated by photoconductive gain. These results cement BiSI as an exciting candidate for high performance photodetector applications and encourage ongoing work in BiSX (X = Cl, Br, I) materials for optoelectronics.

Solution-processed CuSbS2 thin films and superstrate solar cells with CdS/In2S3 buffer layers. ACS Applied Energy Materials, 3(8), 7885-7895.

Herein, an in‐depth experimental investigation into the effect of employing different high resistance metal oxide (HRMO) layers on the quality of the front contact in solar cells with an fluorine‐doped tin oxide (FTO)/(HRMO)/CdS/Sb2Se3/Au device architecture is presented. The application of ZnO or TiO2 HRMO layers between FTO substrates and CdS improves the overall device performance. Short‐circuit current gains of ≈20%, orders of magnitude higher shunt resistances (≈104 Ω cm2), and greatly improved device stabilities—maintaining over 95% of their initial efficiency over 137 days are observed. A suppression of the unfavorable (120) orientation of the photoactive Sb2Se3 layer is observed in devices with HRMO interlayers. The application of HRMO layers is crucial to prevent both ohmic and non‐ohmic current leaks and maintain device stability over time. Cross‐over in the current‐voltage (JV) curves observed in the case of TiO2 indicates the presence of a high barrier for the diode current in these devices. Wavelength‐dependent JV curves coupled with capacitance measurements and simulations show that this barrier can be attributed to a high density of interfacial acceptor states. In contrast, ZnO deposition is found to reduce interface defects and enhance the quality of the front contact, while boosting performance and increasing device longevity.

Antimony chalcogenide, Sb2X3 (X = S, Se), applications greatly benefit from efficient charge transport along covalently bonded (001) oriented (Sb4X6)n ribbons, making thin film orientation control highly desirable – although particularly hard to achieve experimentally. Here, it is shown for the first time that substrate nanostructure plays a key role in driving the growth of (001) oriented antimony chalcogenide thin films. Vapor Transport Deposition of Sb2Se3 thin films is conducted on ZnO substrates whose morphology is tuned between highly nanostructured and flat. The extent of Sb2Se3 (001) orientation is directly correlated to the degree of substrate nanostructure. These data showcase that nanostructuring a substrate is an effective tool to control the orientation and morphology of Sb2Se3 films. The optimized samples demonstrate high (001) crystallographic orientation. A growth mechanism for these films is proposed, wherein the substrate physically restricts the development of undesirable crystallographic orientations. It is shown that the surface chemistry of the nanostructured substrates can be altered and still drive the growth of (001) Sb2Se3 thin films – not limiting this phenomenon to a particular substrate type. Insights from this work are expected to guide the rational design of Sb2X3 thin film devices and other low‐dimensional crystal‐structured materials wherein performance is intrinsically linked to morphology and orientation.