Highly transparent metal selenide counter electrodes for bifacial dye-sensitized solar cells

•Transparent CuMSe (M = Fe, Co) alloys are synthesized by a hydrothermal method.•The transparent CuMSe are used as CE catalysts for bifacial DSSCs.•The CuMSe CEs have superior optical transparencies and activity activities.•Front and rear efficiencies of 7.81% and 5.95% are recorded on the optimal DSSC.

Creation of transparent counter electrode (CE) electrocatalysts for bifacial dye-sensitized solar cells (DSSCs) is a persistent objective for reducing cost of photovoltaic conversion. We present here the experimental realization of highly transparent CuSe CEs by a mild solution method for liquid-junction bifacial DSSCs. The resultant CuSe CEs show superior electrocatalytic activity toward I3− reduction reaction. By optimizing the pH values in synthesizing CuSe electrodes, the maximal front efficiency of 6.21% and rear efficiency of 4.72% are recorded on the corresponding bifacial DSSC. Both catalytic activity and photovoltaic performances can be further elevated by alloying CuSe with Co or Fe, yielding promising efficiencies of 7.81% and 5.38% under front and rear irradiations, respectively.

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