Naphthalimide Molecular-Doped Zinc Oxide Cathode Interfacial Layer Inhibits Charge Trapping in Organic Solar Cells

So far, the recombination center of photogenerated carriers caused by surface defects in ZnO results in poor thickness tolerance and inefficient charge extraction, severely limiting the performance and stability of inverted organic solar cells (OSCs). Therefore, hybrid cathode interfacial layers (CILs) are fabricated in devices by doping naphthalimide-based molecules (NE and NDA) into ZnO, and significantly improved performance and stability are achieved for all tested devices. It is found that doping NE or NDA not only solves the problems of ZnO aggregation and surface defects, but also enhances the ability of charge transfer and lowers the work function of cathode. As a result, the OSCs based on PM6:Y6 with ZnO:NE 1% as a CIL exhibit the highest power conversion efficiency (16.72%), which is better than that of pristine ZnO. The research shows that N atoms in naphthalimide react with Zn ions, and -NH bonds form noncovalent interaction with heteroatoms in the blend, which is conducive to the formation of better chemical bond in hybrid materials and providing more transfer channels for carriers. This study highlights a promising strategy for enhancing the performance of inverted OSCs by the hybrid CIL strategy. It has been found that doping naphthalimide-based molecules (NE or NDA) not only solves problems of ZnO aggregation and surface defects, but also enhances the ability of charge transfer and lowers the work function of the cathode in organic solar cells.image (c) 2023 WILEY-VCH GmbH