Tailoring multifunctional anions to inhibit methanol absorption on a CsPbBr 3 quantum dot surface for highly efficient semi-transparent photovoltaics.

Methyl acetate (MeOAc) is the most used antisolvent in the preparation of perovskite quantum dot (QD) films. However, the hydrolysis of MeOAc results in acetic acid and methanol (MeOH), and the decomposition of the perovskite occurs more easily under acidic and polar conditions. Herein, we report a facile and universal anion modification strategy to inhibit MeOH absorption on a perovskite QD surface and improve the photovoltaic performance of perovskite QD solar cells, which is implemented by incorporating a series of guanidinium salts containing different anions (guanidinium bromide (GuaBr), guanidinium thiocyanate (GuaSCN), and guanidinium acetate (GuaAc)). All anions play a positive role in inhibiting the absorption of MeOH on the QD surface, facilitating charge transfer between perovskite QDs and passivating the defects. Moreover, the regulation of surface chemistry can be optimized by rational tailoring of different anion species. The GuaAc-based devices deliver a PCE of 7.04%, which is the highest value among inorganic CsPbBr ₃ QD solar cells. More importantly, the CsPbBr ₃ QD solar cells exhibit high transparency over the entire visible spectrum region, indicating their promising application in solar windows.