In situ artificial wide-bandgap Cs-based recrystallized-arrays for optical optimization of perovskite solar cells

Coordinated light management as one of the most essential strategies to further improve the power conversion efficiencies (PCEs) of perovskite solar cells (PSCs), which can achieve stronger light trapping, coupling and absorption through submicron nanostructured morphologies relative to planar structure. However, the interfacial preparation of textured-structures has been facing great challenges, which has severely limited the research progress in the field of optical structures of PSCs. Here, in situ growth of inorganic Cs-based perovskite recrystallized-arrays (CPRA) on the perovskite surface was realized by pseudo-halide anion solvent engineering. This preparation procedure of the CPRA is very facile and cost-effective. The induced recrystallization involved in the CPRA synthesis process is non-invasive to the underlying perovskite. It is experimentally and theoretically shown that highly recrystallized-arrays can provide excellent optoelectronic performance. The open circuit voltage (VOC) of the champion PSC modified by this wide-bandgap CPRA can exceed 1.20 V, and the PCE can reach 23.23%. Moreover, this scheme has the function of tuning the bandgap, which can increase the VOC of device up to 1.23 V (PCE 22.12%). The long-term stability of the CPRA-modified PSCs is also prominent based on the inherent lotus hydrophobic properties of the bionic arrays.