Bandgap optimization of submicron‐thick Cu(In,Ga)Se₂ solar cells

Abstract

Abstract Reducing Cu(In,Ga)Se 2 (CIGS) absorber thickness into submicron regime provides an opportunity for reducing CIGS solar cell manufacturing time and cost. However, CIGS with submicron‐thick absorber would suffer strong absorption loss in the long‐wavelength region. In this paper, we report a new fabrication route for CIGS solar cells on soda‐lime glass substrates with different Ga content (0.3 < [Ga]/([Ga] + [In]) < 0.6), all with absorber thicknesses around 0.9 µm. Efficiency of 17.52% has been achieved for cells with high Ga content of [Ga]/([Ga] + [In]) = 41%, which is currently the best reported efficiency for submicron‐thick CIGS solar cells. Unlike the normal‐thickness absorber (2–3 µm) that has an optimal [Ga]/([Ga] + [In]) of ~32%, the increased value of optimal [Ga]/([Ga] + [In]) in submicron‐thick absorber greatly enhances the open‐circuit voltage, by nearly 15% compared with that of samples with Ga content optimized at normal absorber thickness. This large gain in V OC well compensates the absorption loss in the long‐wavelength region and contributes to the enhancement of final solar cell efficiency. Copyright © 2014 John Wiley & Sons, Ltd.