The synergistic effect of dimethyl sulfoxide vapor treatment and C-60 electron transporting layer towards enhancing current collection in mixed-ion inverted perovskite solar cells

Inverted perovskite solar cells (PSCs) have been introduced as better candidate for roll-to-roll printing and scaleup than their conventional configuration counterparts, while their fabrication is technically more demanding. The common light absorbing layer in inverted PSCs is the single cation methylammonium lead iodide (MAPbI(3)) perovskite, whereas mixed-ion perovskites are chemically more stable. In mixed-ion perovskites, where FA (formamidinium) is the main replacement for MA, the electron affinity is larger than in MAPbI3 perovskites, leading to possible barriers against photoelectron collection by the electron transporting layer (ETL). In this paper we report on a mixed-ion (FAPbI(3))(0.83)(MAPbBr(3))(0.17) inverted PSC with improved photocurrent through using a dimethyl sulfoxide vapor treatment of perovskite layer and replacing the conventional [6,6]-phenyl-C-71 butyric acid methyl ester (PC70BM) with C-60/bathocuproine (BCP) as more effective ETL. The treatment of perovskite layer results in reduction of impurity phases of 8-FAPbI(3) and Pbl(2). Photoluminescence and open circuit voltage decay data demonstrate better charge carrier collection by the C-60/BCP compared to the PC70BM ETL, and an electron barrier for the back flow of electrons from ETL to perovskite. Our improvements in perovskite crystalization and electron transfer layer simultaneously lead to increasing the current density from 10 to 21 mA cm(-2).