Type-II InAs/GaAsSb Quantum Dot Solar Cells With GaAs Interlayer
IEEE Journal of Photovoltaics
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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/GaAs1--xSbx 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.