Optimizing CdS Buffer Layer For CIGS Based Thin Film Solar Cell

CdS buffer layer is one of the important factors that affect the conversion efficiency in CIGS-based solar cell. In our PVD CdS process optimization, different sputter powers in the early stage of CdS film growth were tested. Higher sputter power in the early stage of CdS growth improves cell efficiency and widens the process window. AES depth profile reveals a decrease of oxygen content at CdS/CIGS interface. Having fewer oxygen atoms at CdS/CIGS interface reduces the amount of deep acceptors in CIGS and results in improved cell efficiency.