Simultaneous UV and air stability improvement of organic solar cells enabled by carbon-coated zinc oxide as cathode buffer layer

Highlights•Carbon-coated ZnO quantum dots are synthesized and served as the ETL of OSCs•ZnO@C ETL shows better matching energy levels and improves the PCE of OSCs•ZnO@C NP-based OSCs exhibit significantly enhanced air and UV stabilitySummaryZinc oxide nanoparticles (ZnO NPs) are ideal electron transport materials for current high-efficiency organic solar cells (OSCs), but they still face several challenges due to their surface defects and catalytic characteristics. Herein, to address the shortcomings of ZnO NPs, carbon-coated ZnO nanoparticles (ZnO@C NPs) are synthesized. With high hydrophobicity and excellent UV absorption capacity, the thin carbon shell coated on the ZnO NPs can effectively passivate their surface defects, isolate the adsorption of water and oxygen, and inhibit the formation of hydroxyl radicals. Ultimately, the ZnO@C-based PM6:L8-BO OSCs achieve a power conversion efficiency of 17.55%, higher than that of ZnO-based devices (16.92%). What's important, the ZnO@C NP-based OSCs show significantly enhanced air and UV stability. This work highlights the great potential of ZnO@C NPs in fabricating highly efficient, air-stable, and photo-stable OSCs.Graphical abstract