Introducing of MnS passivation layer on TiO2 mesoporous film for improving performance of quantum dot sensitized solar cells

Abstract

Despite great efforts to improve the power conversion efficiency of quantum dot-sensitized solar cells, the cell performances are still far from the maximum theoretical value. Coating a passivation layer on the surface of quantum dot sensitizers has been proven an effective method to enhance cell performance. Herein, a MnS passivation layer is introduced between mesoporous TiO2 and quantum dot sensitizers, rather than being coated on the surface of the quantum dot sensitizers as is generally done. Two kinds of photoanodes, based on TiO2 nanoparticles and {001}-faceted TiO2 nanosheets, are investigated in this work. The results show that introducing a MnS layer induces larger charge transfer resistance and longer carrier lifetime, thus improving cell performance. The photoanode based on {001}-faceted TiO2 nanosheets achieves better power conversion efficiency than that of the TiO2 nanoparticle-based photoanode. A maximum efficiency of 5.01% is acquired, representing a 27.8% relative increase compared with that of the cell without a deposited passivation layer (3.92%). This improvement is attributed to the formation of a cascaded band structure among quantum dots/MnS/TiO2 nanosheets. The present MnS passivation layer achieves the highest improvement in cell efficiency among the limited reports thus far on the surface passivation of TiO2.