Thermo‐Crosslinking Organic Electron Transport Layers for Stable Perovskite Solar Cells Decoded by In Situ Acoustic Resonance

Abstract

ABSTRACT Electron transport layer (ETL) plays a pivotal role in determining the interfacial integrity and operational robustness of n‐i‐p structured perovskite solar cells (PSCs). Conventional tin oxide based inorganic ETLs are often plagued by inherent point defects, while organic small‐molecule ones frequently suffer from limited device efficiency and durability. In this study, we present an innovative molecular design strategy via developing thermo‐crosslinking organic ETLs to overcome these persistent interfacial challenges. Novel organic electron transport materials (ETMs) have been successfully designed by strategically incorporating heat‐inducible cross‐linking triallyl or oxetane functional groups into naphthalene diimide‐based conjugation scaffold, respectively. Such cross‐linkable ETMs exhibit exceptional electronic properties, facile heat‐induced film‐forming capability, and enhanced charge transport. Specifically, featuring optimized energy level alignment and superior surface wettability, oxetane‐functionalized ETL endowed n‐i‐p structured PSCs with a champion power conversion efficiency of 25.23%, among the highest values reported for organic ETL‐based devices. Non‐destructive ultrasonic testing and accelerated aging assessments have been explored for the first time to decode the substantial improvements in interfacial robustness and operational stability under thermal (85°C) and humid conditions (65% relative humidity). This work establishes a versatile material design paradigm for developing robust organic ETLs, paving the way for high‐performance and durable perovskite photovoltaics.