The effects of Na incorporation on the structural and electrical properties of Cu(In,Ga)Se2(CIGS) thin films on polyimide(PI) substrate by low-temperature process are investigated.As shown by XRD,the diffusion of Ga is hindered by Na,the Na incorporation has no influence on the grain size of CIGS thin films.The device performances of solar cells based on CIGS thin films on PI with Na incorporation are remarkably improved due to the improvement of electrical properties of CIGS.The mechanism is that Na increa...