Improving Photovoltaic Performance Using Perovskite/Surface-Modified Graphitic Carbon Nitride Heterojunction

Passivation strategies are considered as one of the most efficient methods to suppress nonradiative recombination of organic–inorganic lead halide perovskite solar cells (PSCs), leading to tremendous photovoltaic performance. An innovative 2D polymer, graphitic carbon nitride (g-C₃N₄), as well as various organic groups (amino, sulfonic, nitrato, and hydroxy group), are widely used as passivation agents, according to the previous reports. Anchoring g-C₃N₄ and the aforementioned organic groups as additives in perovskite can both heal charged defects around the grain boundaries by passivating the charge recombination center. In addition, the crystalline quality can also be enhanced by the incorporation of g-C₃N₄, leading to improved conductivity of perovskite light absorber films that is beneficial for benign charge extraction efficiency. Inspired by the underlining mechanisms, a series of novel passivation molecules, functionalized g-C₃N₄ (F-C₃N₄) with assorted organic groups, is designed herein, yielding a champion power conversion efficiency (PCE) of 20.08% for NO₃-C₃N₄-based p-i-n structure PSC, in comparison with that of PSC without passivation (17.85%). These findings present an efficient strategy to understand and design multiple facets of applications of novel passivation molecules to further improve the PCE of PSCs.