Bifacial quasi-solid-state dye-sensitized solar cell with metal selenide M0.85Se (M = Co, Ni) as counter electrode

To avoid the evaporation and leakage of the liquid electrolyte and increase the long-term stability of the cell, a strategy was developed to construct bifacial dye-sensitized solar cells employing quasi-solid-state electrolyte (BQDSSCs). Two metal selenides with different morphologies, Co0.85Se, which has a foliate structure like the structure of graphene, and Ni0.85Se, which has uniform nanoparticle, were synthesized by a facile one-step hydrothermal method. The proposed BQDSSCs were then constructed using the TiO2 photoanode, polyvinylidene fluoride gel electrolyte, and Co0.85Se or Ni0.85Se as the counter electrode (CE) electrocatalysts. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and Tafel polarization measurements were performed to investigate the electrochemical behavior of the Co0.85Se, Ni0.85Se, and Pt CEs. The results showed that the graphene-like Co0.85Se material exhibited better operational stability, greater charge-transfer ability, and higher electrocatalytic activity for the reduction of I-(3) over bar than the Ni0.85Se nanoparticles. Furthermore, for the BQDSSCs, Co-0.(85) Se yielded the highest power conversion efficiencies (PCE) of 8.33% and 4.79% under front and rear irradiations, respectively, in comparison with the front and rear efficiencies of 7.44% and 4.05% for Pt and 7.23% and 4.16% for Ni0.85Se CEs, respectively. The BQDSSC device based on the Co0.85Se CE exhibited good long-term stability with only a 5% drop in power conversion efficiency after 1000 h of one-sun soaking. Consequently, graphene-like Co0.85Se was considered to be an ideal material for constructing cost-effective BQDSSCs. (C) 2019 Elsevier Ltd. All rights reserved.