Dynamic study of photo-generated charge transport in BiI3 and Cs3Bi2I9

Abstract

The article examined the optoelectronic properties of thin films made from BiI3 and Cs3Bi2I9, which were potential materials for use in solar cells. The films' photocurrent density-time responses were measured and compared, revealing that BiI3 generated higher photocurrent than Cs3Bi2I9. To investigate the differences in optoelectronic properties further, IMPS, PEIS, and SPS measurements were conducted. Results from the IMPS and PEIS measurements showed that BiI3 exhibited much higher charge separation, transfer, and collection compared to Cs3Bi2I9, which could explain the higher photocurrent in BiI3. However, a faster trapping and detrapping process and a quicker charging/discharging process in BiI3 increased the possibility of interface electron/hole recombination. The surface photovoltage (SPV) phase spectroscopy results indicated that a significant increase in the SPV response intensity in the BiI3 film further demonstrated improved surface charge concentration due to better separation and transfer of photo-induced electron-hole pairs.