Vertical Bi2Se3 flake array as a Pt-free counter electrode for dye-sensitized solar cells

In dye-sensitized solar cells (DSSCs), the catalytic activity and electrical conductivity of the counter electrodes (CEs) is of great importance for the increase of power conversion efficiency (PCE). Although Pt is the most widely used material for CEs of DSSCs, the high price and low abundance of Pt severely limit its application on a large scale and alternative materials are highly desired. In this paper, Bi2Se3 films of vertically aligned flake arrays fabricated by the vapor deposition technique are exploited as Pt-free CEs in DSSCs. Thanks to the excellent surface conductivity and the large number of catalytic active sites of Bi2Se3 flakes, the DSSC with a Bi2Se3 vertical flake array CE exhibited higher PCE than that with regular Pt CEs. This work provides an opportunity to develop practical Pt-free CEs which could facilitate the large-scale application of DSSCs.