Variation in the Photocurrent Response Due to Different Emissive States in Methylammonium Lead Bromide Perovskites

Thin films and crystals of methylammonium lead bromide (MAPbBr3) perovskites have strong photoluminescence (PL). Previous studies have shown that the emission arises from different states. However, the role of these states in the performance of a solar cell has not been reported. We have used photocurrent and photoluminescence microscopies (PCM and PLM) to investigate the correlation between the photocurrent (PC) and the PL behavior in the different regions of MAPbBr3 thin film solar cells. Our results show that the PC and the PL responses from the different regions in the thin film show poor correlation compared to the correlation between those of a high efficiency GaAs solar cell. Furthermore, we establish a relationship between the different emissive states and the PC and the PL responses. Out of the two emissive states at 2.34 and 2.28 eV that have been reported, only the state at 2.34 eV has a dominant contribution to the PC. Our results suggest that the emission at 2.28 eV is related to traps, which can lower the performance of the solar cells. Finally, the correlation analysis of the PC and the PL responses we have presented can be used in any solar cell made from direct band gap semiconductor to identify the loss channels in the device.