Surfactant-assisted colloidal size and charge control in perovskite solutions for high-performance and stable solar cells

Solution-based lead halide perovskites have achieved remarkable success in both solar cell performance and market potential. However, limited attention has been given to the colloidal properties of perovskite precursor solutions, which are critical for achieving high performance. This study introduces a method to control colloidal charge and size in perovskite solutions using surfactants, thereby enhancing both solar cell performance and stability. The surfactant dodecyltrimethylammonium bromide (DTAB), featuring a positively charged ammonium head group and a long alkyl chain, induces the formation of smaller, positively charged perovskite colloids. These modified colloids promote slow, homogeneous crystallization, resulting in high-quality perovskite films with low defect densities. Importantly, we established for the first time the relationship between perovskite colloid charge and substrate surface charge. As a result, we achieved a power conversion efficiency (PCE) of 24.50% for FAPbI₃-based perovskite solar cells (PSCs) under 1 SUN conditions, and a 39.01% indoor PCE for 1.67 eV wide-bandgap-based PSCs under 1000 lx LED illumination. Our findings provide critical insights into colloidal–substrate interactions, offering guidance for the development of high-performance PSCs suitable for both outdoor and indoor applications.