Synergistic defect passivation and strain compensation toward efficient and stable perovskite solar cells

Rational interface engineering is essential for minimizing interfacial nonradiative recombination losses and enhancing device performance. Herein, we report the use of bidentate diphenoxybenzene (DPOB) isomers as surface modifiers for perovskite films. The DPOB molecules, which contain two oxygen (O) atoms, chemically bond with undercoordinated Pb2+ on the surface of perovskite films, resulting in compression of the perovskite lattice. This chemical interaction, along with physical regulations, leads to the formation of high-quality perovskite films with compressive strain and fewer defects. This compressive strain-induced band bending promotes hole extraction and transport, while inhibiting charge recombination at the interfaces. Furthermore, the addition of DPOB will reduce the zero-dimensional (0D) Cs4PbBr6 phase and produce the two-dimensional (2D) CsPb2Br5 phase, which is also conducive to the improvement of device performance. Ultimately, the resulting perovskite films, which are strain-released and defect-passivated, exhibit exceptional device efficiency, reaching 10.87% for carbon-based CsPbBr3 device, 14.86% for carbon-based CsPbI2Br device, 22.02% for FA0.97Cs0.03PbI3 device, respectively. Moreover, the unencapsulated CsPbBr3 PSC exhibits excellent stability under persistent exposure to humidity (80%) and heat (80 oC) for over 50 days.