Enhanced electrical properties in 2D perovskites via the bridging effect of SnS1-xO2x for perovskite solar cells with efficiency exceeding 24%

Enhancing the electrical properties of two-dimensional (2D) perovskite layer at the interface between 3D perovskite and hole transport layer (HTL) is of great significance in improving the power conversion efficiency (PCE) and stability of n-i-p 2D/3D perovskite solar cells (PSCs). Herein, SnS1-xO2x is applied to enhance the electrical properties of 2D perovskite and hole transport layer (HTL) in 2D/3D PSCs by the bridging effect. SnS1- xO2x significantly promotes the carrier transport in 2D (BA)2PbI4 layer via Sn-I bonding at SnS1-xO2x/ (BA)2PbI4 interface as well as reduced trap density and improves the hole transfer from (BA)2PbI4 to HTL by optimizing interface energy level alignment and making the I and Pb atoms in the 2D (BA)2PbI4 drop out of the valence band maximum (VBM). In addition, SnS1- xO2x also enhances the conductivity and hydrophobicity of spiro-OMeTAD HTL. As a consequence, a champion efficiency as high as 24.5% with a high open-circuit voltage of 1.23 V is achieved on optimized PSCs, which is one of the highest PCEs of 2D/3D PSCs. Furthermore, unencapsulated PSC shows a remarkable stability, retaining 94.5% of its initial PCE after 1680 h of storage in air with a relative humidity of 20-40%. In addition, the optimized PSCs also exhibit excellent thermal stability and light stability.