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 bilayer metal Bi/Cu thin film with different atomic ratios as precursor to in-situ fabricate CuBiI4 perovskite-like film with controlled Bi gradient at room temperature. This structure can significantly affect the photoinduced charge carrier dynamic of the resulting products. Next, a series of transient surface photovoltage (TSPV) measurements have been carried out to investigate the photoinduced charge carrier dynamics of such CuBiI4 and CuBiI4: organic hybrid thin films. It reveals that the gradually decreased Bi content from ITO to CuBiI4 can help the photoinduced charge carrier transportation. Finally, a champion PCE of 1.10% has been obtained from 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 dynamic 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 assembly of solar cell devices.