Built-In Potential and Operational Stability of Nonfullerene Organic Solar Cells

Many progresses have been made in the advancement of solution-processable high-performance organic solar cells (OSCs), offering an encouraging alternative photovoltaic (PV) technology option to traditional solar cells. The solution processing capability provides OSCs with great fabrication flexibility for new device concepts, cell architectures, and applications including lightweight large-area transparent and flexible PV modules. The unique transparency and flexible features also add an attractive artistic aspect to emerging OSCs for use on curved surfaces, portable electronics, and indoor appliances. However, the stability of the OSCs is still less than satisfactory compared with the conventional inorganic semiconductor solar cells. This work discusses the improvement of the operational stability of OSCs through analyses of the important issues of 1) unbalanced charge mobility, 2) vertical stratification in the bulk heterojunction, and 3) built-in potential across the photoactive layer, and retaining a stable built-in potential for enhancing the operational stability of OSCs.