A novel p-type and metallic dual-functional Cu–Al2O3 ultra-thin layer as the back electrode enabling high performance of thin film solar cells

Increasing the open-circuit voltage (Voc) along with the fill factor (FF) is pivotal for the performance improvement of solar cells. In this work, we report the design and construction of a new structure of CdS/CdTe/Al2O3/Cu using the atomic layer deposition (ALD) method, and then we control Cu diffusion through the Al2O3 atomic layer into the CdTe layer. Surprisingly, this generates a novel p-type and metallic dual-functional Cu–Al2O3 atomic layer. Due to this dual-functional character of the Cu–Al2O3 layer, an efficiency improvement of 2% in comparison with the standard cell was observed. This novel dual-functional back contact structure could also be introduced into other thin film solar cells for their efficiency improvement.