In this paper, the effect of p-n junction additives via blending p-type semiconductors (NiO and CuI) with n-type TiO2 in polymer electrolyte on quasi-solid-state DSSCs is studied. The conduction mechanism of DSSCs modified with random p-n junctions has been investigated by FTIR, SEM, UV Vis and electro-chemical analysis. The results indicate that the CuI-TiO2 p-n blend modified polymer electrolyte reaches the maximum ionic conductivity of 6.44 mS cm(-1), which is almost twice over than that of pure-TiO2 modified one. From photovoltaic study, it is found that introducing CuI-TiO2 and NiO-TiO2 p-n blends in polymer electrolyte can obviously improve electron recombination and light-to-electric conversion efficiency of DSSCs. The conversion efficiency of CuI-TiO2 p-n blend modified DSSC is 3.34%, which is much higher than that of pure TiO2 modified device (1.76%). It is also demonstrated that the photovoltaic properties of DSSCs directly depends on the ratio of p-type CuI and n-type TiO2 in the p-n blends and the optimal conversion efficiency of 4.27% is obtained at CuI:TiO2 ratio of 4:1. (C) 2014 Elsevier B.V. All rights reserved.