Highly Efficient and Stable Wide‐Bandgap Perovskite Solar Cells via Strain Management

Abstract Wide‐bandgap (WBG) perovskite solar cells (PSCs) with high performance and stability are in considerable demand to boost tandem solar cell efficiencies. Perovskite bandgap broadening results in a high barrier for enhancing the efficiency of PSCs and phase segregation in perovskite. In this study, it is shown that the residual strain is the key factor affecting the WBG perovskite device efficiency and stability. The dimethyl sulfoxide addition helps lead halide with opening the layer spacing to form intermediate phases that provide more nucleation sites to eliminate lattice mismatch with organic components, which dominates the strain effects on the WBG perovskite growth in a sequential deposition. By minimizing the strain, 1.67 and 1.77 eV nip devices with record efficiencies of 22.28% and 20.45%, respectively, can be achieved. The greatly suppressed phase segregation enables the devices with retained 90–95% of initial efficiency over 4000 h of damp stability and 80–90% of initial efficiency over 700 h of maximum‐power‐point (MPP) stability. Besides, the 1.67 eV pin devices can achieve a competitive 22.3% efficiency with considerable damp‐heat, pre‐ultraviolet (pre‐UV) aging and MPP tracking stability according to IEC 61215. The final efficiency of more than 28.3% for the perovskite/Si tandem is obtained.