Performance and stability of mixed FAPbI3(0.85)MAPbBr3(0.15) halide perovskite solar cells under outdoor conditions and the effect of low light irradiation

We demonstrate for the first time, the real lifetime response of mixed halide perovskite solar cells (PSCs) for > 1000 h under outdoor conditions and the exceptional photoresponse observed at low-light intensities attributed to the ionic-electronic nature of the material. The investigated devices were fabricated by utilizing mixed perovskites containing formamidinium (FA) and methylammonium (MA) cations, in a one step solution-process method through a solvent engineering approach. The devices' architecture is FTO/TiO2 (blocking layer) TiO2 (mesoporous)/FAPbI(3(0.85))MAPbBr(3(0.15))/Spiro-OMeTAD/Au. Notably, low short circuit current (J(sc)) was observed at low light intensities ( < 50 W/m(2)) together with high open circuit potential build-up, which resulted in high PCEs. This response is in agreement with a double electronic-ionic transport model of the halide perovskite where the ionic component dominates at low light intensities and the electronic component dictates at high light irradiances. Our results highlight the exceptional stability of mixed MA/FA mesoscopic PSCs when operated for > 1000 h under real outdoor conditions and the strong ionic component observed at low light irradiation.