Novel insight into the function of PC61BM in efficient planar perovskite solar cells

A thin PC61BM buffer layer (BL) has been introduced between TiO2 electron transporting layer and perovskite absorber in n-i-p planar perovskite solar cells (PSCs). We have found that the elastic nature of the PC61BM BL promotes the formation of porous Pbl(2-x)Cl(x) thin film with loose structure, which is vital in the following formation of high quality, uniform perovskite films with large grain size. In addition, it has been demonstrated that the thin PC61BM BL also flattens the TiO2 surface, passivates the defects or dangling bands parasitizing on the TiO2 surface, and optimizes the device band alignment. As a result, the device efficiency has been enhanced dramatically from 8.37% to 15.44%. Moreover, devices show a good stability over 400 h and reproducibility in 20 pieces fabricated with the same procedure, which implies that this finding is benefit for fabricating highly efficient PSCs. We introduced a thin PC61BM buffer layer between the TiO2 electron transport layer and the perovskite absorber in n-i-p planar perovskite solar cells, which facilitates the construction of a porous Pbl(2-x)Cl precursor film, and thus promotes the following realization of high quality, uniform perovskite films with large grain size and improves the solar cell efficiency significantly. (C) 2016 Elsevier Ltd. All rights reserved.