8.3% Efficient copper zinc tin sulfoselenide solar cells processed from environmentally benign solvent

Forming kesterite thin films directly from solution is a promising method for inexpensive photovoltaic electricity generation. Recently, we reported 4.1% efficient CZTSSe devices processed from a mixed precursor solution of Cu(CH3COO)2·H2O, ZnCl2, SnCl2·2H2O, and thiourea dissolved in dimethyl sulfoxide (DMSO) [1], an environmental benign solvent. Here, by modifying the precursor solution preparing procedure, a power conversion efficiency of 8.3% with a current density of 31.1mA/cm², an open circuit voltage of 0.44 V, and a fill factor of 0.60 was achieved from a device with an active area of 0.43 cm² without an antireflection coating. The enhanced device performance is due to complete redox reaction between copper and tin precursors which resulted in better absorber material film. Our results demonstrate that highly efficient kesterite solar cells can be realized from simple molecular precursor solution in environmental benign solvent, making this method the most promising approach for low cost earth abundant solar cells.