1. Introduction
As one of the important light-to-electricity convertors, dye sensitized solar cells (DSSCs) have attracted significantly atten-tions since its first report [1] due to its low cost. Nowadays, there searches focus on the further increase of the DSSC energy conversion efficiency. The physical–chemical factors that affect the DSSC efficiency mainly include light harvesting ability and electron diffu-sion length. To date, many works devoted to increasing the electron diffusion length and the energy conversion efficiency by construc-ting different photoanode structures [2,3].