Solvent engineering based on triethylenetetramine (TETA) for perovskite solar cells processed in ambient-air

Solvent engineering as a crucial factor in determining the photovoltaic performance of perovskite solar cells has attracted much attention in recent years. Herein, we treat PbI2 and perovskite films with isopropyl alcohol, acetone, diethyl ether and dichloromethane, as standard solvents, in a modified two-step method. Meanwhile, triethylenetetramine (TETA) is introduced as a new reagent in solvent engineering for perovskite solar cell devices. Structural, optical and photovoltaic characteristics of the TETA-treated perovskite films are compared with those of the ones treated with different solvents. A shiny, pinhole-free and full-coverage texture with sufficiently large grain sizes is obtained in the presence of TETA, suggesting an efficient solvent engineering for perovskite layers. Moreover, the results reveal that residual PbI2 is completely removed and converted to a crystalline perovskite film. Amongst the PSC devices engineered with various solvents, the TETA-treated film exhibits a 55% increase in photoconversion efficiency compared to the control device with no solvent engineering.