Air-stable lead-free hybrid perovskite employing self-powered photodetection with an electron/hole-conductor-free device geometryElectronic supplementary information (ESI) available: Details of the crystalline peak positions, additional optical absorption results, compositional features and electrical measurements are provided in the ESI with quoted references wherever necessary. See DOI: 10.1039/c8nr08959k

In this study, we have demonstrated the fabrication of one of the few lead-free perovskite photodetectors reported to date. In particular, we fabricated the photodetector based on a methylammonium bismuth iodide, MA 3 Bi 2 I 9 (MABI), structure that works under a self-powered mode of operation. The optoelectronic properties of the photodetector were investigated systematically. The photoresponse of the photodetector was carefully studied and compared with the literature, which demonstrated the capability of the MABI structure for detecting light at a very low incident irradiance of 10 μW cm −2 . Also, it exhibited a fast and reproducible response speed along with high photosensitivity (∼10 5 ) and detectivity (∼10 12 Jones) at low operating voltages (0 V and 0.8 V) through the large effective device area. It was also revealed that the MABI photodetector had good stability after storage for two months at ambient conditions. It is therefore concluded that our photodetector fabricated with a MABI perovskite structure using a simple geometry has great potential to further improve the optoelectronic properties when proper electron/hole-transporting layers are fused for proper charge extraction. This will have significant benefits for next-generation cost-competitive optoelectronic technology to address the scalability issue. We have demonstrated the fabrication of one of the few lead-free perovskite self-powered photodetectors reported to date.