Efficient p–n Heterojunction Perovskite Solar Cell without a Redundant Electron Transport Layer and Interface Engineering

We report an electron transport layer-free perovskite solar cell (PSC) without interface engineering, whose key is a p–n heterojunction consisting of ITO/n-type FA0.9Cs0.1PbI3–xClx/p-type spiro-MeOTAD/Ag. The naturally matched energy levels between FA0.9Cs0.1PbI3–xClx and ITO make interface engineering unnecessary. The FA0.9Cs0.1PbI3–xClx film has a wide antisolvent processing window, favoring large-area production. The self-seeding growth method regulates the energy levels and work function of the FA0.9Cs0.1PbI3–xClx film via modulating the shape and distribution of residual PbI2. Interface band bending is confirmed by double-side photoluminescence (PL) measurement. Reduced PL is introduced for unambiguous charge transfer analysis without interference caused by different absorbance. Accordingly, enhanced ITO/perovskite interface energy level alignment and device performance (efficiency of 17.48% and Voc of 1.02 V) are demonstrated. Such simplified but efficient PSCs featuring a wide antisolvent processing window have great potential in practical applications.