Improving the characteristics of intermediate-band solar cell devices using a vertically aligned InAs/GaAsSb quantum dot structure

This study demonstrates the feasibility of improving the optical properties of a vertically aligned quantum dot (QD) structure and the performance of a quantum dot intermediate band solar cell (QD-IBSC) by capping a GaAsSb layer on the InAs QDs. Experimental results indicate that dot-size uniformity is significantly improved due to the strain modification in the evolution of the successive vertically aligned dot layer growth. A solar cell device with an InAs/GaAsSb columnar dot structure increases the short-circuit current density (Jsc) by 8.8%, compared to a GaAs reference cell. This dot structure also increases quantum efficiency by up to 1200 nm through the absorption of lower-energy photons. The InAs/GaAsSb QD-IBSC also improves the open-circuit voltage (Voc), indicating a reduction in misfit defect density and recombination current density. The results of this study confirm the ability of a columnar InAs/GaAsSb QD structure to enhance the device performance.

► Optical and material properties of InAs/GaAsSb columnar dot were first studied. ► The TEM images show the improvement of InAs/GaAsSb columnar QD volume uniformity. ► The EQE of QD-IBSC revealed an extended wavelength range to 1200 nm. ► The InAs/GaAsSb QD-IBSC demonstrates improvements in both Jsc and Voc.