Accelerated Sequential Deposition Reaction via Crystal Orientation Engineering for Low-Temperature, High-Efficiency Carbon-Electrode CsPbBr₃ Solar Cells

Low-temperature, ambient processing of high-quality CsPbBr3 films is demanded for scalable production of efficient, low-cost carbon-electrode perovskite solar cells (PSCs). Herein, we demonstrate a crystal orientation engineering strategy of PbBr2 precursor film to accelerate its reaction with CsBr precursor during two-step sequential deposition of CsPbBr3 films. Such a novel strategy is proceeded by adding CsBr species into PbBr2 precursor, which can tailor the preferred crystal orientation of PbBr2 film from [020] into [031], with CsBr additive staying in the film as CsPb2Br5 phase. Theoretical calculations show that the reaction energy barrier of (031) planes of PbBr2 with CsBr is lower about 2.28 eV than that of (020) planes. Therefore, CsPbBr3 films with full coverage, high purity, high crystallinity, micro-sized grains can be obtained at a low temperature of 150 degrees C. Carbon-electrode PSCs with these desired CsPbBr3 films yield the record-high efficiency of 10.27% coupled with excellent operation stability. Meanwhile, the 1 cm(2) area one with the superior efficiency of 8.00% as well as the flexible one with the champion efficiency of 8.27% and excellent mechanical bending characteristics are also achieved.