Band alignment by ternary crystalline potential-tuning interlayer for efficient electron injection in quantum dot-sensitized solar cells

Abstract

We developed a facile way to enhance electron injection efficiency in CdSe based quantum dot-sensitized solar cells (QDSCs) by introducing a potential-tuning interlayer composed of ternary CdS_1−xSe_x quantum dots (QDs) between TiO₂ film and CdSe QDs. A suitable band structure for electron injection was obtained when the composition of Se was 0.43 in the CdS_1−xSe_x interlayer. The TiO₂/CdS_0.57Se_0.43/CdSe QDSCs achieved a photocurrent density 17.8% higher than conventional TiO₂/CdS/CdSe QDSCs. The enhanced performance is owing to the tuned energetic driving force simultaneously adequate for both exciton dissociation at CdS_1−xSe_x/CdSe interface and electron injection at TiO₂/CdS_1−xSe_x interface. The electron injection also benefited probably from reducing the lattice mismatch between TiO₂ film and CdSe QDs by inserting a crystalline CdS_1−xSe_x interlayer. Our findings indicate that introducing a ternary crystalline potential-tuning interlayer with specifically designed band alignment is a promising strategy to enable efficient electron injection in QDSCs.