Growth and characterization of CIGS thin films by plasma-assisted and thermal-assisted Se vapor selenization process

In this work, we investigate the material growth of the electrodeposited Cu/In/Ga stacked layers selenized by a plasma-assisted Se vapor selenization (PASVS) process at various substrate heating temperatures. For comparison, a merely thermal-assisted Se vapor selenization (TASVS) process is also tested. The PASVS process can help enhance the decomposition of Cu-In-Ga mixed phase and also the formation of Cu-Se and In-Se binary phases when the sample is selenized at 150 °C. However, the use of PASVS process aggravates the element indium loss at the same temperature. Results also indicate that the PASVS process helps to activate the early formation of Ga-Se phase during selenization at 250 °C. The PASVS process generates a porous surface structure with certain CuGaSe2 phase near the surface region at 350 °C. With the increase of selenization temperature, the film selenized by the PASVS process is prone to a grain structure, while it is a polygonal structure in the case of TASVS. The PASVS process is more able to yield a pure CIGS phase with moderate Ga incorporation at a temperature of 550 °C.