▎ 摘　　要

A counter electrode (CE), which acts as an efficient catalyst, plays a pivotal role in dye-sensitized solar cells (DSSCs). Graphene doped by heteroatoms has been regarded as a material having a high reduction catalytic activity to develop efficient Pt-free alternative CE. However, the doping effects accounting for such a catalytic activity remain unknown. In this study, by means of density functional theory calculations, we determined the band gaps, formation energies, and regions of charge-induced impurities to examine the possibilities of B-doped, N-doped, and B-N co-doped graphene (BNG) sheets to replace platinum as CE. Our results demonstrated that the B-N co-doped graphene (BNG) is suitable to be used for CE owing to its small band gap, small formation energy, and having appropriate region of charge-induced impurities. In addition, we considered the iodide reduction reaction on the negatively charged BNG sheet. After injecting two extra electrons, the I-2 molecule can strongly adsorb on the BNG surface and the I-2 decomposition can be achieved with a small activation energy. A theoretical analysis of the obtained results provides us with some useful guidelines for identifying low-cost and effective CEs in the DSSC devices.