Capping vertically aligned InGaAs/GaAs(Sb) quantum dots with a AlGaAsSb spacer layer in intermediate‐band solar cell devices

Abstract

AbstractThis study demonstrated the feasibility of fabricating a highly stacked vertically aligned InGaAs/GaAs(Sb) quantum dot (QD) structure with an AlGaAsSb spacer layer for improving the device performance of QD intermediate‐band solar cell (QD‐IBSC) devices. The power‐dependent photoluminescence measurements of the proposed structure revealed a blueshift in the QD ground‐state emissions when the excitation power was increased, indicating the formation of an intermediate band inside the QD structure. Capping the InGaAs QDs with a GaAsSb layer prevented the QDs from collapsing because there was less In–Ga intermixing between the QDs and GaAsSb layer. In addition to maintaining the QD structure, the carrier lifetime was extended by tuning the energy band alignment of the InGaAs/GaAsSb QD structure. Inserting the AlGaAsSb layer into the spacer layer increased the band gap, which in turn increased the open‐circuit voltage of the QD‐IBSC. The QD‐IBSC in this work shows an extension of external‐quantum efficiency by up to 1200 nm (compared with a GaAs reference cell) through the absorption by QDs and increased the open‐circuit voltage from 0.67 to 0.70 V by adopting the AlGaAsSb spacer layer. These results confirm that adopting a columnar InGaAs/GaAs(Sb) QD structure with a AlGaAsSb spacer layer can enhance the performance of QD‐IBSC devices. Copyright © 2016 John Wiley & Sons, Ltd.