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

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 CdS1-xSex 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 CdS1-xSex interlayer. The TiO2/CdS0.57Se0.43/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 CdS1-xSex/CdSe interface and electron injection at TiO2/CdS1-xSex interface. The electron injection also benefited probably from reducing the lattice mismatch between TiO2 film and CdSe QDs by inserting a crystalline CdS1-xSex 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.