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.

Automated summary

In order to produce efficient and low-cost carbon-electrode perovskite solar cells (PSCs), it is necessary to process high-quality CsPbBr3 films at low temperatures. By introducing CsBr species into the PbBr2 precursor, the crystal orientation of the PbBr2 film can be adjusted from [020] to [031], with the CsBr additive remaining in the film as CsPb2Br5 phase. The reaction energy barrier between (031) planes of PbBr2 and CsBr is found to be lower by 2.28 eV compared to (020) planes. As a result, CsPbBr3 films with full coverage, high purity, high crystallinity, and micro-sized grains can be obtained at a low temperature of 150 degrees C. Carbon-electrode PSCs with these CsPbBr3 films demonstrate a record-high efficiency of 10.27% and excellent operation stability. Additionally, superior efficiencies of 8.00% for a 1 cm(2) area cell and 8.27% for a flexible cell with excellent mechanical bending characteristics are also achieved.