Optimization of CIS window layers and scale-up for large area sub-module application

The CIS heterojunction window layer has been optimized for improved solar cell performance. The window layer is a combination of two layers: (i) a CdS layer deposited by the solution growth method; and (ii) a ZnO layer deposited by low-pressure chemical vapor deposition (LPCVD). The transmission versus wavelength data shows that the short wavelength transmission is controlled by the CdS thickness, while the long wavelength transmission is strongly influenced by the free carrier absorption in the ZnO film. The effect of the window layer on CIS device performance is seen in the quantum efficiency (QE) versus wavelength measurements. The CdS layer affects the short wavelength QE response, while changes in the ZnO layer affect the infrared response. Using the optimized window layers, CIS devices with efficiencies greater than 10% have been fabricated. Both the CdS and ZnO processes have been scaled-up for large area CIS submodule application