Regulating Crystallization in Wide-Bandgap Perovskite with Removable Additives for an Expanded Processing Window Contributes to Efficient Tandem Solar Cells

Abstract

Perovskite solar cells (PSCs) have demonstrated significant potential in next-generation photovoltaics, with perovskite-organic tandem solar cells (TSCs) showing promise in surpassing the Shockley-Queisser limit of single-junction devices. However, achieving high-quality wide-bandgap (WBG) perovskite films remains challenging due to crystallization control, defect minimization, and film uniformity issues. In this work, we investigate using removable additives to regulate the crystallization process of WBG perovskites. With higher melting and boiling points, these additives delay solvent evaporation, expanding the processing window of the solution process and promoting more controlled nucleation and crystallization. The resulting perovskite films exhibited improved crystal uniformity, lower defect densities, reduced non-radiative recombination, and suppressed halide phase segregation. These improvements enable a high open-circuit voltage (VOC) of 1.370 V for a 1.85 eV WBG perovskite front cell, one of the highest reported. Combined with a narrow-bandgap organic layer, we achieve perovskite-organic TSCs with a power conversion efficiency of 23.55%. Our findings highlight the effectiveness of additive engineering in enhancing WBG perovskite films, paving the way for more efficient and scalable TSCs.