Unprecedented conversion efficiency has been demonstrated for perovskite solar cells (PSCs), however, their stability and reliability continue to be challenge. Here, an effective and practical method is demonstrated to overcome the device stability issues in PSCs. A CF4 plasma treatment method is developed that results in the formation of a robust C-F x layer covering the PSC device, thereby, imparting protection during the operation of solar cell. PSCs exposed to fluorination process showed excellent stability against water, light, and oxygen, displaying relatively no noticeable degradation after being dipped into water for considerable time period. The fluorination process did not have any impact on the morphology and electrical property of the top Spiro-OMeTAD layer, resulting in a conversion efficiency of 18.7%, which is identical to that of the pristine PSC. Under the continuous Xe lamp (AM 1.5G, 1 sun) illumination in ambient air for 100 h, the fluorinated PSCs demonstrated 70% of initial conversion efficiency, which is 4000% higher than that of the pristine PSC devices. We believe this breakthrough will have significant impact on the transition of PSCs into real world applications.
Keywords: Plasma; fluorination; hydrophobicity; perovskite; protection; stability.