Bismuth-based perovskites are promising candidates for highly stable halide perovskites with low toxicity. Here, we report the synthesis of a series of bismuth iodide-based perovskites with different primary, secondary, and tertiary ammonium cations and study their structural, thermal, and optical properties, and the likelihood of photodetection. Interestingly, the variation of A-site organic ammonium cations, with different interlayer spacings between adjacent bismuth iodide monolayers, has exotic effects on the diffraction patterns and morphological structures of the perovskite crystals. Thermogravimetric analysis reveals the highest thermal stability of tertiary ammonium-based bismuth perovskite with a decomposition temperature of 385 °C. The branched primary ammonium-based photodetector has photo-responsivity roughly two and four times faster than that of secondary and tertiary ammonium-based devices, respectively. These findings provide insight into the importance of A-site cation engineering for structural modulation and tailoring the optoelectronic properties of bismuth-based perovskites for emerging optoelectronic devices.
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