Modification of band alignment at interface of AlyGa1-ySb/AlxGa1-xAs type-II quantum dots by concentrated sunlight in intermediate band solar cells with separated absorption and depletion regions

TL;DR

This paper investigates how concentrated sunlight modifies band alignment at AlGaSb/GaAs quantum dot interfaces, enhancing carrier dynamics and increasing solar cell efficiency by 15% through two-photon absorption effects.

Contribution

It introduces a novel intermediate band solar cell design with separated absorption and depletion regions and analyzes the impact of concentrated sunlight on band alignment and efficiency.

Findings

Band alignment at quantum dot interfaces is modified by concentrated sunlight.

Two-photon absorption leads to increased recombination lifetime and photocurrent.

Efficiency improves by 15% at 300-sun concentration compared to standard GaAs cells.

Abstract

We propose a new intermediate band GaAs solar cell comprising an AlxGa1-xAs absorber with built-in GaSb type-II quantum dots (QDs) [a gradual AlxGa1-xAs absorber with built-in AlyGa1-ySb QDs (0<x=y<0.40) as a variant] separated from the depletion region. We study the modification of the band alignment at type-II interface by two-photon absorption of concentrated sunlight. Our calculation shows that photogenerated carriers produce localized exciton-like electron-hole pairs spatially separated at QDs. Local field of such pairs may essentially modify potential barrier surrounding QDs, increase recombination lifetime of mobile carriers and additional photocurrent generated by twophoton absorption. Concentration of about 300-sun pushes by 15% up the conversion efficiency as compared to the efficiency of the reference single junction GaAs solar cell without QDs.