RbCs(MAFA)PbI3 perovskite solar cell with 22.81% efficiency using the precise ions cascade regulation

Abstract

By controlling the doping ratio of Rb+ and Cs+ ions in the perovskite precursor solution, the morphology of the perovskite film is effectively improved, and the δ phase (non perovskite phase) and PbI2 phase in the rod-shaped structure of the film are transformed into α phase (perovskite phase), and the formation of impurity phase is inhibited. At the same time, the addition of mixed Rb+ and Cs+ ions can be embedded in the “ion cascade” of (MA0.5FA0.5) PbI3 films, and a gradient potential is formed. Rb+ and Cs+ ions can effectively reduce the non radiation recombination and trap density of RbxCsx(MA(1-2x)/2 FA(1-2x)/2) PbI3 films, and form larger grains and smaller surface roughness in the perovskite films, which are conducive to the formation of better contact between the perovskite film and the electron transport layer, and result in larger open circuit voltage, short circuit current density and filling factor. Compared with the PCE of undoped (MA0.5FA0.5) PbI3 perovskite solar cells (PCE = 17.15%,VOC = 1.22 V, JSC = 18.75 mA/cm2, FF = 75), the open circuit voltage of Rb0.2Cs0.2(MA0.3FA0.3)PbI3 perovskite solar cells with doping concentration of 20% is increased to 1.25 V, the short circuit current density is increased to 23.70 mA/cm2 and the filling factor is 77%, the power conversion efficiency is 22.81%, and the increase of PCE is nearly 33%, which is the highest reported efficiency of a four component RbxCsx(MA(1-2x)/2 FA(1-2x)/2) PbI3 perovskite solar cell so far.