Development, Challenges, and Vision for Fullerene‐Based Electron Transport Layer in Perovskite Solar Cells: An Industrial Perspective

The power conversion efficiency (PCE) of perovskite solar cells (PSCs) has reached 27.18%, benefiting from the rapid advance of self‐assembled monolayers and fine manipulation of crystallization kinetics of perovskite. However, the further development of PSCs is hindered by the lagging electron transport layers (ETLs) that fullerene ETLs are dominated. To tackle this problem, great efforts have been devoted to improving the properties of fullerene ETLs, such as enhancing defect passivation, tuning energy levels, suppressing self‐aggregation, and so on, for elevating the efficiency and stability of PSCs. In this review, the recent advances in fullerene ETLs are summarized. For thermal‐evaporation deposited fullerene ETLs, the thickness and thermal annealing are identified as key factors to be optimized, and novel multifunctional fullerene derivatives are developed. For solution‐processed fullerene ETLs, new fullerene derivatives and effective methods are developed to address the issues that impede the PCE and stability of PSCs. This review aims to provide an overview and deep understanding of fullerene‐based ETLs for PSCs. Finally, the strengths and drawbacks of these two film‐deposition methods are discussed from a commercial perspective, and possible strategies for further development of fullerene ETLs are provided.