Improving Thermal Stability of Perovskite Solar Cells by Suppressing Ion Migration

Ion migration presents a formidable obstacle to the stability and performance of perovskite solar cells (PSCs), hindering their progress toward commercial feasibility. Herein, the degradation mechanism of PSCs caused by iodide ion migration, which leads to abnormal changes in photoluminescence transients at the buried interface of perovskite films, is investigated. In light of this problem, a novel strategy is proposed to mitigate ion migration by introducing poly(2‐vinylnaphthalene) into poly[bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine] as the hole transport layer with improved ion‐blocking capability. Consequently, this layer effectively reduces defect concentration, suppresses ion migration, and modulates energy level alignment, leading to an impressive efficiency exceeding 23% for doctor‐bladed FAPbI 3 PSCs. Moreover, the corresponding unencapsulated devices demonstrate remarkable durability, maintaining over 80% of their initial value after undergoing rigorous stress tests in accordance with the International Electrotechnical Commission 61215 standard for temperature, humidity, and illumination. These tests include 1000 h of thermal cycling and a long‐term operational test lasting 600 h under maximum power point tracking.