Gradient formation and charge carrier dynamics of CuBiI4 based perovskite-like solar cells†
Designing lead-free inorganic perovskite or perovskite-like structure materials and researching the corresponding photoinduced charge carrier dynamics are always promising due to both the environment and power conversion efficiency considerations. In this work, we intelligently employ a bilayer metal Bi/Cu thin film with different atomic ratios as the precursor to fabricate a CuBiI4 perovskite-like film in situ with a controlled Bi gradient at room temperature. This structure can significantly affect the photoinduced charge carrier dynamics of the resulting products. Next, a series of transient surface photovoltage (TSPV) measurements are carried out to investigate the photoinduced charge carrier dynamics of such CuBiI4 and CuBiI4:organic hybrid thin films. The results reveal that the gradually decreasing Bi content from ITO to CuBiI4 can facilitate the photoinduced charge carrier transportation. Finally, a champion PCE of 1.10% is obtained for an ITO/CuBiI4:polythieno[3,4-b]-thiophene-co-benzodithiophene (PTB7)/Au solar cell device. In particular, we find an exact negative correlation of the defined parameter L (the defined value for evaluating the photoinduced charge carrier dynamics in TSPV measurements) with the corresponding PCE of various devices for the first time, which may pave a new way for evaluating the potential photoelectric and photovoltaic performances of new materials without the assembly of solar cell devices.