Degradation Mechanisms Associated with Electron‐Blocking Layers in Inverted Perovskite Solar Cells

The operational stability, especially under thermal cycling conditions, of perovskite solar cells (PSCs) based on different electron-blocking layers (EBLs) is still missing. Here, we investigate the device performance of PSCs based on representative EBLs of NiO_x, PTAA, and 2PACz as well as the degradation mechanism using operando grazing incidence wide-angle X-ray (GIWAXS) measurements. 2PACz-based devices achieve an impressive PCE of 25.74% (certified 25.34%), which is significantly higher than 23.35% for NiO_x-based and 24.57% for PTAA-based PSCs, attributed to the reduced trap density, prolonged charge carrier lifetime, and suppressed non-radiative recombination. In addition, the 2PACz-based devices exhibit excellent stability under light soaking (>1500 h of T₉₀ lifetime) and rapid solar-thermal cycling conditions (no PCE degradation). Operando GIWAXS demonstrates that this stability originates from a relatively lower lattice distortion at both the buried side and the surface side of the perovskite layer of the 2PACz-based device under the temperature variation during solar-thermal cycling conditions. This work provides experimental evidence for the rational selection of EBL materials and highlights the interface regulation for constructing highly stable perovskite devices.