Aluminum Doped Zinc Oxide as Front Electrode for Rear Emitter Silicon Heterojunction Solar Cells with High Efficiency

Transparent conductive oxide TCO layers of aluminum doped zinc oxide ZnO Al were investigated as a potential replacement of indium tin oxide ITO for the front contact in silicon heterojunction SHJ solar cells in the rear emitter configuration. It was found that ZnO Al can be tuned to yield cell performance almost at the same level as ITO with a power conversion efficiency of 22.6 and 22.8 , respectively. The main reason for the slight underperformance of ZnO Al compared to ITO was found to be a higher contact resistivity between this material and the silver grid on the front side. An entirely indium free SHJ solar cell, replacing the ITO on the rear side by ZnO Al as well, reached a power conversion efficiency of 22.