Thin GaAsSb capping layers for improved performance of InAs/GaAs quantum dot solar cells

摘要: This work reports on the benefits from using thin GaAsSb capping layers (CLs) InAs/GaAs quantum dot (QD) solar cells. The application of such CLs allows tunability QD ground state, switching QD-CL band alignment type I to II for high Sb contents and extending photoresponse beyond 1.5 µm. Two different structures with ~10% ~20% in CL (type-I type-II alignments, respectively) are explored, leading efficiency improvements over a reference cell 20% 10%, respectively. In general, significant increase short-circuit current density (Jsc) is observed, partially due extended photocurrent spectrum additional contribution itself. Particularly, moderate content, an improved carrier collection also found be main reason Jsc increase. Calculations 8×8 k·p method suggest attribution improvement longer lifetimes wetting layer-CL structure transition alignment. Open-circuit voltages (Voc) exceeding that demonstrated under light concentration CLs, which proves Voc not limited by low bandgap CLs. Moreover, highest value obtained content structure, despite higher accumulation strain lower effective bandgap. Indeed, faster power latter case leads even larger than