Graphitic carbon nitride doped SnO2 enabling efficient perovskite solar cells with PCEs exceeding 22%

The energy level alignment and carrier mobility of the charge transport layer are of crucial importance for electron extraction and transport in planar heterojunction perovskite solar cells (PSCs). In this work, a carbon nitride modified SnO2 nanocomposite, SnO2/graphitic carbon nitride (g-C3N4) quantum dots, was designed as the functional electron transport layer (ETL) to precisely regulate the interfacial charge dynamics for high-performance PSCs. It is demonstrated that the g-C3N4 could recast the electronic density distribution around the neighboring SnO2 crystal unit, thus effectively eliminating the oxygen-vacancy-reduced trap centers and promoting the interface and bulk electron transport. Consequently, this carbon nitride modified SnO2 nanocomposite exhibits appropriate electrical properties including suitable energy level alignment and high conductivity. Employing the typical hybrid SnO2-based ETL, a maximum power conversion efficiency (PCE) of 22.13% (V-oc = 1.176 V, J(sc) = 24.03 mA cm(-2), FF = 0.783) can be achieved for planar heterojunction PSCs, with negligible hysteresis and long-term stability (only 10% PCE decay after 1500 h at a relative humidity of 60%). Our work offers a hybrid ETL design strategy to improve the efficiency and stability of PSCs.