OPTIMUM DESIGN AND ITS EXPERIMENTAL APPROACH OF A-SI POLY-SI TANDEM SOLAR-CELL/

A series of technical data on four-terminal a-Si//poly-Si stacked sola r cells has been reported. The developed device has some unique signif icances such as high achievable efficiency, and low cost with almost n o light induced degradation. It has been shown on a poly-Si bottom cel l that an efficiency of 17.2% has been obtained by employing high cond uctivity with wide optical band-gap p-type muc-SiC as a window materia l and n-type muc-SiC as a back ohmic contact with BSF effects. On the optically transparent a-Si top cell, an optimum design has been experi mentally made with the device structure of p muc-SiC/p a-SiC/i a-Si/n muc-Si/ITO, and an efficiency of 7.25% has been obtained with a 100 nm thick i-layer, while the best efficiency is 12.3% for p-i-n single-ju nction solar cell with 500 nm i-layer thickness deviced by Ag back-ele ctrode. With the 100 nm thick ultrathin top cell, a total conversion e fficiency as high as 21.0% has been achieved on a-Si//poly-Si four-ter minal tandem solar cells.