Side‐Chain Engineering of Nickel Naphthalocyanine‐Based Hole‐Transport Materials Realizes >25% Efficiency and Light‐Heat Durable Perovskite Solar Cells

Abstract Hole‐transport materials (HTMs) play an essential role in governing both the efficiency and stability of perovskite solar cells (PSCs). However, it still remains challenging to satisfy these two aspects simultaneously in n–i–p structured PSCs. Here, for the first time, the application of nickel naphthalocyanine (NiNc)‐based HTMs in PSCs is reported. Three NiNc derivatives, namely BuO‐NiNc, HeO‐NiNc, and OcO‐NiNc, are synthesized by modulating the length of alkoxy substituents. The impacts of the alkoxy side‐chain length on the molecular ordering, hole‐transport property, and film morphology of NiNcs are systematically investigated. Comprehensive experimental and theoretical analyses disclose that hexyloxy‐substituted NiNc (HeO‐NiNc) exhibits highly ordered molecular packing and stronger intermolecular interactions, resulting in superior hole transport characteristics. This leads to a champion power conversion efficiency (PCE) of 25.23% for HeO‐NiNc‐based devices, which is the record efficiency reported for metal complex‐based HTMs in PSCs. Moreover, the encapsulated devices employing HeO‐NiNc also exhibit outstanding photo‐thermal durability, retaining over 81% after 1008 h under continuous 1‐sun irradiation at 85 °C (ISOS‐L‐2 protocol). This represents one of the best light‐heat stability among n–i–p PSCs with >25% PCE. This work offers new routes for the development of HTMs in PSCs that simultaneously combine high efficiency and high long‐term stability.