While perovskite solar cells (PVSCs) have drawn intense attention due to their high solar-to-power conversion efficiency (PCE), their practical application is hampered by the poor long-term stability against moisture. Although strategies have been reported to solve this issue, they are introduced during core-device fabrication processes which will increase the risk of introducing unexpected impurities during the fabrication.
In this work, we propose a new scheme of ligand-induced post-device (LPD) modification of perovskite on completely fabricated devices at room temperature to simultaneously improve the performance and stability of PVSCs . The ligand vapors will induce chemical modification in the selected lateral regions particularly that of perovskite layer which prevent the diffusion of water molecules into the protected active perovskite region for enhancing PVSC stability. This post-device treatment could also passivate the surface defects of perovskites in active region for improving the PVSC performance. Interestingly, this LPD modification strategy shows a special ‘stitching effect’, namely repairing the as-fabricated ‘poor devices’ by healing the defects of perovskite in the operation region and significantly improve PCE by over 900%. The work greatly improves the production yield of PVSCs and their module performance as well as the reduction of lead-waste. It should be noted that the off-the-shelf treatment, completely separated from the fabrication process of common perovskite devices, provides a general strategy to improve the stability of different completed perovskite devices (e.g. solar cells, light-emitting diodes, and photodetectors) without introducing any undesirable impurities during device fabrication.
 H. Zhang, X. Ren, X. Chen, J. Mao, J. Cheng, Y. Zhao, Y. Liu, J. Milic, W.J. Yin, M. Grätzel, W.C.H. Choy*, "Improving the stability and performance of perovskite solar cells via off-the-shelf post-device ligand treatment", Energy & Environmental Science, 2018, DOI: 10.1039/C8EE00580J.