The effect of Mn-doped ZnSe passivation layer on the performance of CdS/CdSe quantum dot-sensitized solar cells**Project supported by the National Natural Science Foundation of China (Grant Nos. 61376011, 61704114, 51402141, and 61604086), the Gansu Provincial Natural Science Foundation, China (Grant No. 17JR5RA198), the Fundamental Research Funds for the Central Universities, China (Grant Nos. lzujbky-2018-119 and lzujbky-2018-ct08), and the Fund from

Abstract

ZnSe as a surface passivation layer in quantum dot-sensitized solar cells plays an important role in preventing charge recombination and thus improves the power conversion efficiency (PCE). However, as a wide bandgap semiconductor, ZnSe cannot efficiently absorb and convert long-wavelength light. Doping transition metal ions into ZnSe semiconductors is an effective way to adjust the band gap, such as manganese ions. In this paper, it is found by the method of density functional theory calculation that the valence band of ZnSe moves upward with manganese ions doping, which leads to acceleration of charge separation, wider light absorption range, and enhancing light harvesting. Finally, by using ZnSe doped with manganese ions as the passivation layer, the TiO2/CdS/CdSe co-sensitized solar cell has a PCE of 6.12%, and the PCE of the solar cell increases by 9% compared with the undoped one (5.62%).