Type-Ⅱ InP quantum dots in wide-bandgap InGaP host for intermediate-band solar cells

摘要

We demonstrate type-Ⅱ quantum dots (QDs) with long carrier lifetimes in a wide-bandgap host as a promising candidate for intermediate-band solar cells. Type-Ⅱ InP QDs are fabricated in a wide-bandgap InGaP host using molecular beam epitaxy. Time-resolved photoluminescence measurements reveal an extremely long carrier lifetime (i.e., greater than 30 ns). In addition, from temperature-dependent PL spectra, we find that the type-Ⅱ InP QDs form a negligible valence band offset and conduction band offset of ΔE_c ≈ 0.35 eV in the InGaP host. Such a type-Ⅱ confinement potential for InP/InGaP QDs has a significant advantage for realizing efficient two-step photon absorption and suppressed carrier capture in QDs via Auger relaxation.