Improving the stability and performance of perovskite solar cells: Via off-the-shelf post-device ligand treatment

While metal halide perovskite solar cells (PVSCs) have drawn intense attention due to their high solar-to-power conversion efficiency (PCE), their practical application is hampered by their poor long-term stability against moisture. Although strategies have been reported to solve this issue, these methods are introduced during core-device fabrication processes which will increase the risk of introducing unexpected impurities during the fabrication. Herein, we introduce the first kind of simple post-device ligand (PDL) treatment to significantly improve the PCE of completely fabricated PVSCs from 18.7% to 20.13%. Meanwhile, the stability of the treated devices without any encapsulation remarkably improves, with 70% PCE maintained under ambient conditions after a 500-hour maximum-power-point tracking test, while the control unencapsulated device will completely break down within 100 hours. Equally important is that this post-device treatment shows a special 'stitching effect', namely repairing the as-fabricated 'poor devices' by healing the defects of the perovskite active region, and can improve the PCE by over 900%. We also experimentally and theoretically study the fundamental mechanism of the improvement. Consequently, our approach greatly improves the production yield of high-quality PVSCs and their module performances as well as the reduction of lead-waste. Additionally, the treatment is an off-the-shelf post-device approach that can be integrated into any existing perovskite-device fabrication, offering a general strategy to improve the stability and performance of perovskite optoelectronic devices.