Two-Photon Photocurrent in InGaN/GaN Nanowire Intermediate Band Solar Cells

TL;DR

This paper demonstrates InGaN/GaN nanowire heterostructures on silicon as a cost-effective platform for intermediate band solar cells, achieving two-photon photocurrent and significant efficiency improvements at room temperature.

Contribution

It introduces a novel nanowire quantum-dot-in-nanowire system on silicon for intermediate band solar cells, enabling two-photon current generation with enhanced room temperature performance.

Findings

Up to 19% photocurrent increase at 78 K

Up to 44% photocurrent increase at room temperature

Successful demonstration of two-photon current in nanowire heterostructures

Abstract

Intermediate band solar cells hold the promise of ultrahigh power conversion efficiencies using a single semiconductor junction. Many current implementations use materials with bandgaps too small to achieve maximum efficiency or use cost-prohibitive substrates. Here we demonstrate a material system for intermediate band solar cells using InGaN/GaN quantum-dot-in-nanowire heterostructures grown directly on silicon to provide a lower cost, large-bandgap intermediate band solar cell platform. We demonstrate sequential two-photon current generation with sub-bandgap photons, the hallmark of intermediate band solar cell operation, through vertically stacked quantum dots in the nanowires. Near-infrared light biasing with an 850 nm laser intensity up to 200 W/cm2 increases the photocurrent above and below the bandgap by up to 19% at 78 K, and 44% at room temperature. The nanostructured III-nitride strategy provides a route towards realistic room temperature intermediate band solar cells while leveraging the cost benefits of silicon substrates.