High efficiency a‐Si//poly‐Si tandem solar cell

A series of experimental trials has 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 percent 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 percent 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.