Highly efficient and stable inverted planar solar cells from (FAI)x(MABr)1−xPbI2 perovskites

Abstract

We report highly efficient and stable inverted planar lead mixed-halide (Br, I) perovskite solar cells with a configuration of ITO/poly(3-bromothiophene)/(FA)y(MA)1−yPbBrxI3−x/C60/BCP/Ag (FA: HC(NH2)2+; MA: CH3NH3+). We found that small changes in the composition of (FA)y(MA)1−yPbBrxI3−x have big impact on the material properties and device performance. Appropriate Br-doping enlarges MAPbBrxI3−x's bandgaps and prolongs the life of the excited charge carrier, which leads to higher device open-circuit voltage (VOC). Replacing “MA” with “FA” extends the absorption of (FA)y(MA)1−yPbBrxI3−x which compensates the JSC loss in MAPbBrxI3−x from Br-doping. The optimized perovskite film with a composite of FA0.8MA0.2PbBr0.2I2.8 shows a lifetime of 670ns and a photoelectric response to 830nm, resulting in an enhanced JSC of 22.2mAcm−2, a high FF of 0.80, and an efficiency of 18.1%. In addition, the inverted device based on FA0.8MA0.2PbBr0.2I2.8 showed long-term stability with 80% efficiency remained after 4 months in a glovebox without encapsulation. Our results demonstrate highly efficient and stable inverted planar perovskite solar cells can be achieved by optimizing absorber material composition, which offer a reference for their applications in flexible or tandem solar cells.