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, Co 0.85 Se, which has a foliate structure like the structure of graphene, and Ni 0.85 Se, which has uniform nanoparticle , were synthesized by a facile one-step hydrothermal method . The proposed BQDSSCs were then constructed using the TiO 2 photoanode, polyvinylidene fluoride gel electrolyte, and Co 0.85 Se or Ni 0.85 Se 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 Co 0.85 Se, Ni 0.85 Se, and Pt CEs. The results showed that the graphene-like Co 0.85 Se material exhibited better operational stability, greater charge-transfer ability, and higher electrocatalytic activity for the reduction of I 3 − than the Ni 0.85 Se 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 Ni 0.85 Se CEs, respectively. The BQDSSC device based on the Co 0.85 Se 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 Co 0.85 Se was considered to be an ideal material for constructing cost-effective BQDSSCs.