A hybrid ZnO nanoparticle electron transporting layer for inverted structure organic solar cells with efficiency over 19%

Electron transport layers (ETLs) play a pivotal role in determining the efficiency and stability of inverted structure organic solar cells (OSCs). Zinc oxide nanoparticles (ZnO NPs) are commonly used as ETLs due to their mild deposition conditions and compatibility with flexible plastic substrates, facilitating scalable manufacturing. In this study, we introduce a molecule called NMO, which serves a dual purpose: efficiently dispersing ZnO nanoparticles and acting as a surface modification layer for ZnO NPs thin films. The hybrid ETL created by blending and surface modification with NMO significantly enhances both the efficiency and stability of OSCs. Inverted structure OSCs, based on the PM6:Y6 system and utilizing the hybrid ETL, achieve impressive power conversion efficiency (PCE) of 18.31%. Moreover, these devices demonstrate exceptional stability during shelf storage (T80 = 19,650 h), thermal aging (T80 = 7783 h), and maximum power point tracking (T80 = 3009 h). Importantly, the hybrid ETL exhibits good generality, as all tested OSCs utilizing it display significantly improved efficiencies and stabilities. Notably, a PCE of 19.23% is attained for the PM6:BTP-eC9-based device, marking the highest reported efficiency for inverted single-junction OSCs to date.