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 conver-sion 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].