Abstract
A series of experimental trials have been carried out to realize the high efficiency a-Si//poly-Si tandem solar cell. Employing p type μc-SiC as a wide gap heterojunction window, a-SiC as an interface buffer layer and n type μc-Si as a back ohmic contact layer, 17.2% conversion efficiency has been achieved with the structure of ITO/p μc-SiC/n poly-Si/n μc-Si heterojunction. Utilizing an optically transparent a-Si p-i-n cell as a top cell and inserting an optical coupler between the top and the poly-Si bottom cell, a high total efficiency of 21.0% has been obtained so far on the four-terminal tandem cell. This conversion efficiency value represents a world record for a-Si basis tandem solar cells.
