We selected the above three materials to prepare DSSCs. The TiO2 materials shown in Fig. 1(A) was used to make micro-sphere paste with small pore size, named paste-1; The TiO2 materials shown in Fig. 1(B)was used to make micro-sphere paste with large pore size, named paste-2; and the TiO2 material shown in Fig. 1(D) was used to make nanoparticle paste, named paste-3. Moreover, commercial P25 was also used to prepare paste for comparison, named paste-4.