Cesium carbonate functionalized graphene quantum dots as stable electron-selective layer for improvement of inverted polymer solar cells

Solution processable inverted bulk heterojunction (BHJ) polymer solar cells (PSCs) are promising alternatives to conventional silicon solar cells because of their low cost roll-to-roll production and flexible device applications. In this work, we demonstrated that Cs₂CO₃ functionalized graphene quantum dots (GQDs-Cs₂CO₃) could be used as efficient electron-selective layers in inverted PSCs. Compared with Cs ₂CO₃ buffered devices, the GQDs-Cs₂CO ₃ buffered devices show 56% improvement in power conversion efficiency, as well as 200% enhancement in stability, due to the better electron-extraction, suppression of leakage current, and inhibition of Cs ⁺ ion diffusion at the buffer/polymer interface by GQDs-Cs ₂CO₃. This work provides a thermal-annealing-free, solution-processable method for fabricating electron-selective layer in inverted PSCs, which should be beneficial for the future development of high performance all-solution-processed or roll-to-roll processed PSCs. © 2013 American Chemical Society.