In this paper, the influences of Na on the crystalline and electrical properties of Cu2ZnSnSe4 have been systemically studied. Na was incorporated into the CZTSe films with two different substrates (SiO2/Si and Mo coated Soda-lime-glass) by pulse laser deposition to accurately control the concentration of Na element. The results showed that the sodium incorporation had positive effects on the performances of solar cell based on the as-prepared CZTSe absorber layer, including the open circuit voltage, short circuit current, fill factor and thereby power efficiency. But, with the superfluous alkalis doping, the cell performances decreased quickly, which have been systemically studied to investigate the influences of Na doping on the crystalline and electrical properties of absorber layer and to get the optimal alkalis doping concentration. (C) 2015 Elsevier Ltd. All rights reserved.