Regulating film crystallization kinetics with thiourea additive in Cs2AgBiBr6 solar cells

Cs2AgBiBr6 solar cells have the advantages of non-toxicity and high stability and are regarded as one of the most promising novel solar cells. The crystallization kinetics of the films play a crucial role on the film microstructure and the optoelectronic properties. Herein, thiourea is introduced into the Cs2AgBiBr6 precursor solution as an additive. Fourier transform infrared spectroscopy characterization confirms that thiourea acts as a Lewis base to form an adduct with Ag+, Bi3+. The modified Cs2AgBiBr6 film is used to fabricate solar cells. As a result, the power conversion efficiency and the open-circuit voltage of the optimized device are 1.65% and 1.07 V, significantly higher than the control device (1.04% and 0.89 V). Dark current-voltage, electrochemical impedance spectroscopy, etc, reveal that defects and recombination in the solar cells are inhibited. This work provides an effective method to regulate the crystallization kinetics of Cs2AgBiBr6 film and is helpful for further enhancement of the photovoltaic performance of Cs2AgBiBr6 solar cells.