Passivated Metal Oxide n-Type Contacts for Efficient and Stable Organic Solar Cells

Suppressing trap states and localized electronic states in the forbidden gap of semiconductors as either active layers or contacts is critical to the enhancement of optoelectronic device performance, such as for solar cells, ultrafast photodetectors, field-effect transistors, as well as other optoelectronic applications. In this study, we demonstrate that Lewis bases-passivated metal oxide n-type contacts can effectively improve the performance of organic solar cells (OSCs). OSCs with triethanolamine-passivated ZnO show a two orders of magnitude lower trap density, and thus a higher electron mobility, and three times longer charge carrier recombination lifetime, relative to the devices based on as-cast ZnO. Passivated ZnO universally improves the power conversion efficiency (PCE) of OSCs based on varied active layers. P3HT:PC₇₁BM-based solar cells with passivated-ZnO yield 86% PCE enhancement relative to the control devices based on as-cast ZnO, and PM6:Y6-based devices with passivated-ZnO exhibit PCEs up to 15.61%. Furthermore, light stability of OSCs with passivated-ZnO has also been improved along with enhanced device efficiency. A Lewis base is also efficient to passivate SnO_x contact for solar cells. This study highlights the importance of defect passivation on contact layers for improvement of the efficiency and stability of OSCs and also provides one facile and effective passivation strategy.