A simple strategy to obtain graphitic carbon nitride modified TiO₂layer for efficient perovskite solar cells

The power conversion efficiency (PCE) of perovskite solar cells (PSCs) can be improved through the concurrent strategies of enhancing charge transfer and passivating defects. Graphite carbon nitride (g-C₃N₄) has been demonstrated as a promising modifier for optimizing energy level alignment and reducing defect density in PSCs. However, its preparation process can be complicated. A simple one-step calcination approach was used in this study to prepare g-C₃N₄-modified TiO₂via the incorporation of urea into the TiO₂precursor. This modification simultaneously tunes the energy level alignment and passivates interface defects. The comprehensive research confirms that the addition of moderate amounts of g-C₃N₄to TiO₂results in an ideal alignment of energy levels with perovskite, thereby enhancing the ability to separate and transfer charges. Additionally, the g-C₃N₄-modified perovskite films exhibit an increase in grain size and crystallinity, which reduces intrinsic defects density and extends charge recombination time. Therefore, the g-C₃N₄-modified PSC achieves a champion PCE of 20.00%, higher than that of the control PSC (17.15%). Our study provides a systematic comprehension of the interfacial engineering strategy and offers new insights into the development of high-performance PSCs.