Br Vacancy Defects Healed Perovskite Indoor Photovoltaic Modules with Certified Power Conversion Efficiency Exceeding 36%

Indoor photovoltaics (IPVs) are expected to power the Internet of Things ecosystem, which is attracting ever-increasing attention as part of the rapidly developing distributed communications and electronics technology. The power conversion efficiency of IPVs strongly depends on the match between typical indoor light spectra and the band gap of the light absorbing layer. Therefore, band-gap tunable materials, such as metal-halide perovskites, are specifically promising candidates for approaching the indoor illumination efficiency limit of similar to 56%. However, perovskite materials with ideal band gap for indoor application generally contain high bromine (Br) contents, causing inferior open-circuit voltage (V-OC). By fabricating a series of wide-bandgap perovskites (Cs(0.17)FA(0.83)PbI(3-)(x)Br(x), 0.6 <= x <= 1.6) with varying Br contents and related band gaps, it is found that, the high Br vacancy (V-Br) defect density is a significant reason that leading to large V-OC deficits apart from the well-accepted halide segregation. The introduction of I-rich alkali metal small-molecule compounds is demonstrated to suppress the V-Br and increase the V-OC of perovskite IPVs up to 1.05 V under 1000 lux light-emitting diode illumination, one of the highest V-OC values reported so far. More importantly, the modules are sent for independent certification and have gained a record efficiency of 36.36%.

Automated summary

Indoor photovoltaics (IPVs) are promising for powering the Internet of Things. The power conversion efficiency depends on the match between indoor light spectra and the band gap of the light absorbing layer. Metal-halide perovskites, with tunable band gaps, show potential but high bromine content leads to low open-circuit voltage (V-OC). By introducing iodine-rich compounds, the V-OC of perovskite IPVs can be increased up to 1.05 V under 1000 lux illumination, setting a record efficiency of 36.36%.