2024 年 51 巻 3 号 論文ID: 51-3-03
Polycrystalline Cu(In,Ga)Se2 (poly-CIGS) solar cells are widely studied for their application in thin-film photovoltaics. Single-crystalline CIGS solar cells can potentially address the issues of poly-CIGS solar cells, and we fabricated epitaxial CIGS (epi-CIGS) layers on GaAs substrates using techniques developed for high-efficiency poly-CIGS solar cells such as Ga grading, Na doping, and heat-light soaking. Scanning transmission electron microscopy was used to compare the structural characteristics of poly-CIGS and epi-CIGS solar cells with conversion efficiencies of more than 21%. Both types of solar cells had similar Ga gradient profiles. These observations suggest that grain boundaries in poly-CIGS layers are not the main factor limiting the conversion efficiency of poly-CIGS solar cells.