Multifunctional Zwitterionic Modification of SnO2 in n–i–p Perovskite Solar Cells with Enhanced Fill Factor

SnO2 has been widely employed as the electron transport layer in n–i–p perovskite solar cells owing to its remarkable characteristics, such as easy preparation, high light transmittance, and excellent chemical stability. However, they are characterized by uneven colloidal dispersion, surface oxygen vacancies, and energy misalignment with the perovskite layer. In this study, a multifunctional modification approach was adopted by integrating aminomethanesulfonic acid (AMSA) molecules, characterized by an amphoteric structure, into SnO2. AMSA played a pivotal role in flattening the SnO2 film, ensuring uniform dispersion of SnO2 colloids, preventing nanoparticle aggregation, filling oxygen vacancies, and promoting a more aligned interfacial energy-level arrangement. This facilitated the growth of perovskite films with larger grains on AMSA-modified SnO2, resulting in a decent power conversion efficiency of up to 24.12% and an impressive fill factor of 84.29% for the leading n–i–p device. Notably, the AMSA-SnO2-based device retained 93% of its initial efficiency after 1000 h of continuous 1 sun illumination and maintained 94% of its original value after 4000 h in an air environment without encapsulation.