Crystalline defects in highly efficient widegap Cu(In,Ga)Se2 based solar cells
Speaker: Professor Takeaki Sakurai from Tsukuba University
Cu(In1–x,Gax)Se2 (CIGS) is an excellent material for the application to thin-film solar cells. Its efficiency has exceeded 22.6 % for the device with Ga concentration, x, of ~0.3. Toward the next generation high performance solar cells, securing high quality CIGS films with high Ga concentration is necessary since ideal bandgap energy for single junction solar cell is predicted as 1.4 eV, which corresponds to x of 0.6~0.7. Nevertheless, the loss of the open circuit voltage was observed for the cell with high Ga concentration. For understanding its carrier recombination process, we have studied defects in widegap CIGS solar cells using various characterization techniques, e.g., Admittance, Photo-capacitance, and Photoluminescence. In this presentation, I will discuss relation between deep defects and carrier recombination processes in CIGS layers, and will explain the origin of the defects.
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