Combining a Si solar cell with a high-bandgap top cell reduces the thermalization losses in the short wavelength and enables theoretical 1-sun efficiencies far over 30%. We have investigated the fabrication and optimization of Si-based tandem solar cells with 1.8-eV rear-heterojunction GaInP top cells. The III-V and Si heterojunction subcells were fabricated separately and joined by mechanical stacking using electrically insulating optically transparent interlayers. Our GaInP/Si dual-junction solar cells have achieved a certified cumulative 1-sun efficiency of 29.8% +/- 0.6% (AM1.5g) in four-terminal operation conditions, which exceeds the record 1-sun efficiencies achieved with both III-V and Si single-junction solar cells. The effect of luminescent coupling between the subcells has been investigated, and optical losses in the solar cell structure have been addressed.
Beat Ruhstaller, Urs Aeberhard
Bin Ding, Xianfu Zhang, Bo Chen, Yan Liu
Christophe Ballif, Aïcha Hessler-Wyser, Antonin Faes, Jacques Levrat, Gianluca Cattaneo, Fahradin Mujovi, Umang Bhupatrai Desai, Matthieu Despeisse