Authors: T.H. Wu
Affilation: National Cheng Kung University, Taiwan
Pages: 671 - 674
Keywords: solar cells, 1 eV material, dilute nitride, hetero-junction
Since the high efficiency tandem solar cell sturcture has been reported, the conversion efficiency of triple-junction solar cells would achieve 40% with concentrator. To further enhance the conversion efficiency of solar cells, the fourth-junction is used to decrease the wasting of energy transformation caused by current limiting in tandem solar cells, so that the conversion efficiency of four junction tandem solar cell is expected to achieve up to 45%. Thus, InGaP/GaAs/ InGaAsN/Ge (1.8/ 1.42/ ~1/ 0.7eV) hetero-structures have attracted much attention, recently. In this study, we have grown p-GaAs/i-InGaAsN/n-GaAs double heterojunction solar cell (DHJSC) by AIX200 metalorganic chemical vapor deposition (MOCVD) system. The lattice matched InGaAsN epi-layers were grown at the growth temperature 550oC with DMHy flow rate 3.5×10-3 mol/min and 3.8×10-3 mol/min, respectively. The conversion efficiency of DHJSCs increases form 2.39% to 2.94% with lower nitrogen incorporation instead of less lattice mismatch between epi-layer and substrate, thus, it implies the crystal quality of epi-layer would influence the total conversion efficiency. From the external quantum efficiency spectrum, the absorption region of InGaAsN DHJSCs would reach less than 1 eV. Therefore, this investigation is suitable to be applied on four junction solar cell structure.