Reconstruction of Electron-Selective Interface via\nMultifunctional Chemical Bridging Enables High-Performance Rigid and\nFlexible Perovskite Solar Cells

Interface\nengineering has significantly boosted perovskite solar\ncell efficiency and stability. However, numerous approaches focus\non addressing defects at the interfaces between transport layers while\nneglecting potential issues within the bulk perovskite material. Here,\na multifunctional molecule, sodium lignosulfonate (SL), containing\nthree types of functional groups, was introduced as a chemical bridge\nat the perovskite/SnO<sub>2</sub> interface. The introduced SL bridges\npromote energy level alignment at the perovskite/SnO<sub>2</sub> interface\nand regulate the perovskite crystallization process. Meanwhile, the\ncoordinated interactions between the perovskite components with −OH\nand −SO<sub>3</sub><sup>–</sup> groups on SL, coupled\nwith Na<sup>+</sup> diffusion, effectively passivate defects at the\nburied interface and within the perovskite bulk. As a result, the\nchampion SnO<sub>2</sub>–SL based <i>n-i-p</i> PSC\nachieved power conversion efficiencies of 25.73% and 25.13% on rigid\nand flexible substrates, respectively. Unencapsulated devices maintained\n92.9% of their initial efficiency after 2,550 h of maximum power point-tracking\nunder 1-sun illumination in an inert atmosphere.