Interfacial charge-transfer engineering by ionic liquid for high performance planar CH3NH3PbBr3 solar cells

Abstract

The energy barrier at the CH3NH3PbBr3/TiO2 interface hinders the electron transfer from CH3NH3PbBr3 to compact TiO2 (cp-TiO2). Ionic liquid (IL), that forms dipoles pointing away from TiO2, can adjust the work function of TiO2 resulting in suitable energy level for charge transfer from CH3NH3PbBr3 to TiO2. The time-resolved photoluminescence spectroscopy (TRPL) measurements confirm faster electron transfer from the CH3NH3PbBr3 film to TiO2 after modification by IL. Solar cells based on IL modified cp-TiO2 demonstrate efficiency of ∼6%, much higher than the devices (0.2%) fabricated using untreated cp-TiO2 as the electron transport layer.