cPCN-Regulated SnO₂ Composites Enables Perovskite Solar Cell with Efficiency Beyond 23

Efficient electron transport layers (ETLs) not only play a crucial role in promoting carrier separation and electron extraction in perovskite solar cells (PSCs) but also significantly affect the process of nucleation and growth of the perovskite layer. Herein, crystalline polymeric carbon nitrides (cPCN) are introduced to regulate the electronic properties of SnO₂ nanocrystals, resulting in cPCN-composited SnO₂ (SnO₂-cPCN) ETLs with enhanced charge transport and perovskite layers with decreased grain boundaries. Firstly, SnO₂-cPCN ETLs show three times higher electron mobility than pristine SnO₂ while offering better energy level alignment with the perovskite layer. The SnO₂-cPCN ETLs with decreased wettability endow the perovskite films with higher crystallinity by retarding the crystallization rate. In the end, the power conversion efficiency (PCE) of planar PSCs can be boosted to 23.17% with negligible hysteresis and a steady-state efficiency output of 21.98%, which is one of the highest PCEs for PSCs with modified SnO₂ ETLs. SnO₂-cPCN based devices also showed higher stability than pristine SnO₂, maintaining 88% of the initial PCE after 2000 h of storage in the ambient environment (with controlled RH of 30% ± 5%) without encapsulation.