The development of cost-effective, functional materials that can be efficiently used for sustainable energy generation is highly desirable. Herein, a new molecular precursor of bismuth (tris(selenobenzoato)bismuth(III), [Bi(SeOCPh)₃]), has been used to prepare selectively Bi or Bi₂Se₃ nanosheets via a colloidal route by the judicious control of the reaction parameters. The Bi formation mechanism was investigated, and it was observed that the trioctylphosphine (TOP) plays a crucial role in the formation of Bi. Employing the vapor deposition method resulted in the formation of exclusively Bi₂Se₃ films at different temperatures. The synthesized nanomaterials and films were characterized by p-XRD, TEM, Raman, SEM, EDX, AFM, XPS, and UV–vis spectroscopy. A minimum sheet thickness of 3.6 nm (i.e., a thickness of 8–9 layers) was observed for bismuth, whereas a thickness of 4 nm (i.e., a thickness of 4 layers) was observed for Bi₂Se₃ nanosheets. XPS showed surface oxidation of both materials and indicated an uncapped surface of Bi, whereas Bi₂Se₃ had a capping layer of oleylamine, resulting in reduced surface oxidation. The potential of Bi and Bi₂Se₃ nanosheets was tested for overall water-splitting application. The OER and HER catalytic performances of Bi₂Se₃ indicate overpotentials of 385 mV at 10 mA cm^–2 and 220 mV, with Tafel slopes of 122 and 178 mV dec^–1, respectively. In comparison, Bi showed a much lower OER activity (506 mV at 10 mA cm^–2) but a slightly better HER (214 mV at 10 mA cm^–2) performance. Similarly, Bi₂Se₃ nanosheets were observed to exhibit cathodic photocurrent in photoelectrocatalytic activity, which indicated their p-type behavior.

Inorganic lead halide perovskite solar cells with mixed halides have achieved reasonable power conversion efficiency with the advantage of enhanced stability. In this work, we report the fabrication of an all-inorganic cesium lead bromoiodide based planar perovskite solar cell with a ZnO electron transport layer. The method described herein includes the use of one step spin coating solution processing using a solvent mixture (DMF + DMSO) to avoid the solubility issues of CsPbBr₂I perovskite in DMF. The substrate temperature during spin coating was found to be a critical parameter to generate the required crystalline morphology of the perovskite thin films. Post-annealing of the as-deposited perovskite film at 275 °C led to the formation of the cubic phase of CsPbBr₂I with an optical band gap of 2.06 eV. Interestingly, cubic shaped CsPbBr₂I morphology was obtained via single-step spin-coating processing that otherwise required two-step solution deposition of the hybrid perovskite. The best performing devices achieved 4.8% power conversion efficiency with minimal hysteresis and enhanced thermal and photo-stability. Owing to enhanced thermal and photo-stability, inorganic perovskites appear as viable alternatives to hybrid organic–inorganic perovskites for solar cell applications.

A new organo tin complex has been synthesized and used as a single source precursor for the synthesis of tin selenide nanosheets and deposition of thin films.