Solution-Processed Bismuth(III)-Based Halide Perovskites as Absorber Materials for Photovoltaic Applications

Bismuth(III) halide perovskites are promising alternative absorber materials to commonly used organolead- and organotin-based perovskites due to the low toxicity and ambient stability.^[1] In this work, hybrid organic-inorganic bismuth(III) halide perovskites based on methylammonium (CH₃NH₃⁺, MA⁺) as A-site cation and halide counter ions (I^-, Cl^-) incorporated on the X-site of the perovskite structure were investigated using bismuth(III) halides (BiI₃, BiCl₃) and methylammonium iodide (MAI) as starting compounds. The perovskite absorber materials (MA₃Bi₂I₉, MA₃Bi₂I_9-xCl_x) were prepared in a low-temperature solution-based processing route following a one-step and two-step procedure.^[2,3] The absorber materials were evaluated with regard to their photovoltaic performance in organic (PEDOT:PSS) as well as in planar (c-TiO₂) and meso-structured (c-TiO₂/mp-TiO₂) perovskite solar cell architecture (Fig. 1). In addition, the perovskites were characterized optically (UV/VIS spectroscopy, light microscopy), structurally (X-ray diffraction), and morphologically (atomic force microscopy).