Type-II InAs/GaAsSb Quantum Dot Solar Cells With GaAs Interlayer

Abstract

One of the primary challenges facing quantum dot (QD)-based intermediate band solar cells is the short lifetime of charge carriers (∼1 ns). To investigate this, InAs QD/GaAs 1-x Sb x quantum well (QW) solar cells (SCs) with a 2-nm GaAs interlayer between the QDs and QW were fabricated for x = 0, 0.08, 0.14, and 0.17, respectively. Time-resolved photoluminescence measurements demonstrated prolonged carrier lifetimes up to 480 ns for the type-II SCs with x ࣙ 14%. This improvement in carrier lifetime is assigned to the GaAs interlayer that reduces the wavefunction overlap between the electrons accumulated in the QDs and holes in the QW, and hence limits the possible emission pathways. External quantum efficiency measurements were performed to analyze the SC performance. An order of magnitude improvement was observed in the QD region (900-1200 nm) for the type-II SCs and is linked to the prolonged carrier lifetime.Index Terms-Intermediate band solar cells (IBSCs), molecular beam epitaxy, quantum dot (QD) solar cells.

HRTEM Study of Size‐Controlled Bi Quantum Dots in Annealed GaAsBi/AlAs Multiple Quantum Well Structure

“…Using the TEM sample thickness of 60 nm, the QD's areal density in a single QW is 2.1 × 10 10 cm −2 . The determined density for Bi QDs is several times higher than in MOCVD‐grown GaAsBi/GaAs MQW and comparable to other composition QDs in GaAs system (1.26 × 10 10 cm −2 for InAs‐QD/GaAsBi, 4.3 × 10 10 cm −2 for InAs‐QD/GaAsSb, and 2.9 × 10 10 cm −2 for InAs‐QD/GaAs …”

Altering the Optical Properties of GaAsSb-Capped InAs Quantum Dots by Means of InAlAs Interlayers

“…3b and hence holes captured in the QW may tunnel through the InAlAs layer making less probable the type II emission. For a thicker In 0.15 Al 0.85 As interlayer (40 Å and 60 Å), the tunneling is further reduced but the electron and hole wavefunction overlap is substantially reduced favoring the recombination of electrons in GaAs with holes in GaAsSb [13]. The optical transition of InAs/GaAsSb QDs can be tailored to the type of application requiring either short or long lifetimes.…”

“…The use of InAlAs layers may be of interest to engineering the type of radiative recombination. For type II transition, the insertion of InAlAs will increase the carrier lifetime [13] and the energy separation between the fundamental and first excited states [14–16]. Moreover, the insertion of an InAlAs layer between InAs QDs and GaAsSb is expected to decrease In segregation and suppress In and Ga atoms intermixing between the InAs QDs and the GaAsSb SRL and reduce further the QD strain [17].…”

Gas Sensitivity of In0.3Ga0.7As Surface QDs Coupled to Multilayer Buried QDs

“…III-V semiconductor quantum dots (InAs, InGaAs, InP, etc.) formed in self-organized growth mode are typical nanomaterials, widely used in optoelectronic fields like laser, photodetector, LED, and solar cell [5][6][7][8][9]. Lately, InGaAs (InP) surface quantum dots (SQDs) have also attracted much attention in the application field of gas sensing materials [10][11][12].…”