Solution-Induced surface modification and secondary grains growth for high-performance and stable perovskite solar cells

Enhancing the quality of perovskite layer and refining the interface between the perovskite layer and the hole transport layer (HTL) represent pivotal strategies for optimizing the efficiency and stability of perovskite solar cells (PSCs). We accomplished this by employing a solution isopropanol (IPA), capable of selectively dissolving residual unreacted methylammonium and formamidine salts on the perovskite surface while preserving the integrity of lead iodide. Through control of the immersion time, we facilitated secondary crystal growth on the top of perovskite film. The resultant treated film exhibited a markedly suitable bandgap position and a diminished presence of residual trips. The IPA-treated sample led to a noteworthy photovoltaic conversion efficiency (PCE) of 23.34 %, compared to 21.46 % efficiency for untreated control sample. Furthermore, under sustained illumination at AM 1.5G with 25 % relative humidity, the uncovered IPA-treated sample retained an impressive 92 % of their initial efficiency after 1000 h. Further scrutiny revealed that this solution-based treatment effectively passivated trips, enhanced perovskite film quality, established novel built-in electric fields, and mitigated charge carrier recombination. This work provides a simple perovskite film treatment approach that does not require complex molecular engineering and can be applied not only to PSCs but also to other perovskite optoelectronic devices.