Improved conversion efficiency of InN/p-GaN heterojunction solar cells with the InON quantum dots interlayer

Abstract

Heterojunction solar cells were formed by deposition of sputtered InN thin films on p-type GaN/sapphire substrate. The indium oxynitride (InON) quantum dots (QDs) interlayer were inserted between the InN and p-GaN films for improving the conversion efficiency of heterojunction solar cells. The InN/InON QDs/p-GaN heterojunction solar cells exhibited a high open-circuit voltage of 2.29 V, short-circuit current density of 1.64 mA/cm2 and a conversion efficiency of 1.12% under AM 1.5G illumination. The two-fold increase of power conversion efficiency compared to the sample without InON QDs was due to the increasing short-current density. A shoulder peak at −0.08 V was found in the high-frequency (60–100 kHz) C-V characteristic curves correspond to the carrier capture and emission in the shallow defect state of oxygen vacancy in the InON QDs. The oxygen vacancy not only exists inside the InON QDs but also generate the interface state in the interface between the InON QDs and p-GaN to provide a carrier transport path. The increase of the power conversion efficiency of InN/InON QDs/p-GaN heterojunction solar cells is attributed to build a carrier transport channel that provided by the InON QDs interlayer.