The energy of the sunlight that reaches the Earth’s surface is about 8000 times higher than the current global energy consumption, making solar energy one of the most abundant renewable energy sources. Photovoltaics researchers are extremely motivated to tackle this tough energy problem and aim to achieve the most cost-effective means for sunlight-to-electricity conversion. The research mostly focuses on organic photovoltaics (OPVs) with lightweight and thin organic semiconductor layers. OPV commonly sandwiches a bulk heterojunction blend of organic electron donors and electron acceptors between a transparent electrode and a metal electrode. The quality of the critical interfaces, involving organic/electrode and organic/inorganic heterojunctions, therefore significantly influences the overall device performance. Especially, the contact interface at the organic-metal oxide heterojunction is important to determine the device performance, however, it is lacking efficient control methods.

In a joint exploration at the University of Electronic Science and Technology of China and Zhejiang University, researchers demonstrate that a nanometer thin fullerene interfacial layer can effectively improve the organic-metal oxide heterojunction of inverted OPV cells. As a result, devices with fullerene treated ZnO_x exhibit a high fill factor of 0.77 for PTB7-Th:PC₇₁BM blend based inverted OPV cells, with the best photon conversion efficiency as high as 11.3%.

This study elucidates the unique structure-property correlation of effective interfacial materials to their corresponding photovoltaic behaviors, as well as exemplifies useful materials to engineer the organic-inorganic heterojunction. It adds valuable insights for advancing state-of-the-art organic materials and electronics.