Pre-annealing treatment for high-efficiency perovskite solar cells via sequential deposition

Abstract

<h2>Summary</h2> Grain boundaries (GBs) have been shown to initiate metal halide perovskite degradation under light, moisture, and/or heat stresses due to the existence of various defects, making them extremely vulnerable in perovskite solar cells (PSCs). Although various post-treatments have been proven to be effective in repairing GBs, preventing the degradation from perovskite GBs remains an extremely difficult challenge. We report here a generic pre-annealing treatment for reconstructing sequentially deposited perovskite crystallites and GBs. With this strategy, robust GBs are created upon defect suppression with preferred oriented large perovskite grains. As a result, the resultant n-i-p-structured PSCs deliver an impressive power conversion efficiency of nearly 25% and an extremely high fill factor of 85.5%. The unencapsulated cells maintain 81% of their initial efficiencies after 1,000 h of continuous operation at maximum power point at about 55°C in an inert atmosphere, showing greatly improved light stability.