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Ruddleson–Popper (RP) perovskites have emerged as a class of material inheriting the superior optoelectronic properties of two materials: perovskites and 2D materials. The large exciton binding energy and natural quantum well structure not only make these materials ideal platforms to study light–matter interactions but also render them suitable for fabrication of various functional optoelectronic devices. Nanoscale structuring and morphology control have led to semiconductors with enhanced functionalities. Nanowires of semiconducting materials are extensively used for important applications like lasing and sensing. However, catalyst and template‐free scalable growth of nanowires of 2D perovskites has remained elusive. In this paper, a facile approach for morphology‐controlled growth of nanowires of 2D perovskite, (BA)₂PbI₄, is demonstrated. Additionally, it is shown that the photoluminescence (PL) from the nanowires is highly polarized with a polarization ratio as large as ≈0.73, which is one of the largest reported for perovskites. It is further shown that the photocurrent from the hybrid nanowire/graphene device is also sensitive to the polarization of the incident light with the photocurrent anisotropy ratio of ≈3.62 (much larger than the previously reported value of 2.68 for perovskites), thus demonstrating the potential of these nanowires as highly efficient photodetectors for polarized light.

Organic–inorganic halide perovskites are intrinsically unstable when exposed to moisture and/or light. Additionally, the presence of lead in many perovskites raises toxicity concerns. Herein, a thin film of barium zirconium sulfide (BaZrS₃), a lead‐free chalcogenide perovskite, is reported. Photoluminescence and X‐ray diffraction measurements show that BaZrS₃is far more stable than methylammonium lead iodide (MAPbI₃) in moist environments. Moisture‐ and light‐induced degradations in BaZrS₃and MAPbI₃are compared by using simulations and calculations based on density functional theory. The simulations reveal drastically slower degradation in BaZrS₃due to two factors—weak interaction with water and very low rates of ion migration. BaZrS₃photodetecting devices with photoresponsivity of ≈46.5 mA W⁻¹are also reported. The devices retain ≈60% of their initial photoresponse after 4 weeks under ambient conditions. Similar MAPbI₃devices degrade rapidly and show a ≈95% decrease in photoresponsivity in just 4 days. The findings establish the superior stability of BaZrS₃and strengthen the case for its use in optoelectronics. New possibilities for thermoelectric energy conversion using these materials are also demonstrated.

Rhenium disulfide (ReS₂) differs fundamentally from other group‐VI transition metal dichalcogenides (TMDs) due to its low structural symmetry, which results in its optical and electrical anisotropy. Although vertical growth is observed in some TMDs under special growth conditions, vertical growth in ReS₂is very different in that it is highly spontaneous and substrate‐independent. In this study, the mechanism that underpins the thermodynamically favorable vertical growth mode of ReS₂is uncovered. It is found that the governing mechanism for ReS₂growth involves two distinct stages. In the first stage, ReS₂grows parallel to the growth substrate, consistent with conventional TMD growth. However, subsequent vertical growth is nucleated at points on the lattice where Re atoms are “pinched” together. At such sites, an additional Re atom binds with the cluster of pinched Re atoms, leaving an under‐coordinated S atom protruding out of the ReS₂plane. This under‐coordinated S is “reactive” and binds to free Re and S atoms, initiating growth in a direction perpendicular to the ReS₂surface. The utility of such vertical ReS₂arrays in applications where high surface‐to‐volume ratio and electric‐field enhancement are essential, such as surface enhanced Raman spectroscopy, field emission, and solar‐based disinfection of bacteria, is demonstrated.