IMPROVED PERFORMANCE OF LOW-TEMPERATURE SELENIZED CuINSe2 SOLAR CELLS BY Na SUPPLY

摘要

The structural properties of CuInSe2 films grown at different vacuum–selenized annealing temperatures were systematically investigated by Raman scattering. It is found that the most intense Raman band for the film deposited at 220 °C is around 261 cm–1, indicating the presence of intermediate phase CuxSe. With increasing the growth temperatures from 220 to 400 °C, the disappearance of CuxSe phase suggests that the formation of chalcopyrite and CuAu-ordering CuInSe2 phases should preferably proceed through Se-poor phases as CuxSe matrix. The post-treatment process introduction of CuInSe2 films by external Na doping could eliminate metastable CuAu-ordering phase via evaporation of an NaF precursor. Moreover, the cell using such additional process shows a total-area efficiency of about 8%. The results suggest that the Na addition should reduce charged defects due to the presence of CuAu–ordered phase domains at grain boundaries, and thus improve device performance.