Abstract
Co-evaporated perovskite solar cells (PSCs) have demonstrated outstanding properties, such as great scalability, intrinsic stability, high-power conversion efficiency (PCE), and fabrication adaptability even on rough surfaces. At present, MAPbI(3) is the most used co-evaporated perovskite due to the complexity of forming multi-component compositions by thermal evaporation. Even though PSCs with high PCEs have been obtained, the MAPbI(3) bandgap (similar to 1.60 eV) is not ideal for multijunction devices. In this work, we propose a facile method to increase the bandgap of co-evaporated MAPbI(3) (similar to 1.60 eV) through a MABr-based treatment. The best MABr-treated perovskite composition films show a bandgap of 1.66 eV (MAPb(Br0.18I0.82)(3)) and exhibit good spectral stability under continuous 1-sun illumination at the ambient conditions of 28 degrees C and 70% relative humidity. This hybrid method works efficiently for thick co-evaporated MAPbI(3) films (similar to 750 nm), which is unusual for hybrid processes. The n-i-p PSCs built from the MAPb(Br0.18I0.82)(3) films exhibit a blue-shifted external quantum efficiency and a V-oc increase of similar to 30 mV as compared to the pure MAPbI(3) PSCs, in agreement with the bandgap widening observed in the films. This hybrid method to crete wide bandgap perovskites can be universally applied to MAPbI(3) deposited on both flat and textured surfaces and shows great promise for its integration in monolithic tandems.