Effects of passivation treatment on performance of CdS/CdSe quantum-dot co-sensitized solar cells

Carrier recombination can greatly reduce the efficiencies of quantum-dot sensitized solar cells (QDSSCs). This work aims to find a general preparation route to reduce carrier recombination in QDSSCs. The effects of a series of passivation treatments on CdS/CdSe quantum-dot (QD) co-sensitized solar cells are investigated. The QDs were synthesized on a nanoporous TiO2 electrode by the successive ionic layer adsorption and reaction processes. The different types of treatment included a blocking layer, a fluoride-ion coating, a ZnS coating, annealing, a TiO2 scattering layer and an Au counterelectrode. The power conversion efficiency was observed to become three times larger after treatment. The effectiveness of each treatment method is as follows in descending order: blocking layer ≅ TiO2 scattering layer > Au counterelectrode > F− ions and ZnS coatings > annealing. The best cell yields a current density of 14.6 mA/cm2 and a respectable power conversion efficiency of η = 3.11% under AM 1.5 sun. The passivation procedure makes a useful general guide for researchers for the preparation of QDSSCs.

► Used a series of treatments to passivate quantum-dot sensitized solar cells
► Efficiency increased by a factor of three after going through all the treatments
► Contribution to efficiency due to each treatment determined quantitatively
► Obtained a best efficiency of 3.11%