Exploiting an alternative of the Pt-based counter-electrode materials for the triiodide reduction reaction has become a major interest in the fundamental research of dye-sensitized solar cells. Transition-metal selenides have recently been demonstrated as promising non-precious metal electrocatalysts for the triiodide reduction reaction. Herein, we prepared a series of transition-metal selenides via a free-reductant solvothermal method and used them as counter-electrodes in high efficiency dye-sensitized solar cells. The electrochemical results showed that these selenides had excellent catalytic activity for the reduction of the triiodine/iodine couple, and except for MoSe2, the conversion efficiencies of the corresponding dye-sensitized solar cells were comparable to the sputtered Pt counter-electrode. Theoretical investigation clearly revealed that the unsatisfactory performance of MoSe2 mainly originated from the processes of adsorption and charge-transfer. These findings can help to better understand the electrocatalytic processes and thus offer some useful guidelines to develop more efficient electrochemical catalysts.