Abstract
Polycrystalline CuIn1-xGaxSe2 (CIGS) solar cell with efficiency of 20.3% was reported using three-stage co-evaporation on soda-lime glass substrate. It has been known that Na diffusion from the soda-lime glass into the CIGS absorber is one of the key factors to achieve the maximum cells efficiency. In this thesis, we study to alternative Na incorporation methods, including (1) Sputtering Na doped Molybdenum film (Mo:Na) and (2) Na implantation. In the first part, we use Mo/Mo:Na multilayer structure to serve as cell back contact and provide CIGS with Na. Na doped by Mo:Na film with increasing thickness can efficiently eliminate the current blocking, barrier for light current at forward bias, and increase the open circuit voltage than Na doped by SLG due to better compensate VSe with the help of oxygen. In the second part, Ion implantation was applied for quantitative and spatial control of Na distribution in CIGS films. In the annealing process, the formation of donor type defects due to defects interaction decreases the carrier density of CIGS. Implantation on a heated substrate can efficiently reduce implant-induced lattice displacement and lead to an enhancement in electrical properties of device.