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

ABSTRACT 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 T ₉₀ 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.