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Long-Lived 1D Excitons in Bright CdTe Quantum Wires

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journal contribution
posted on 14.01.2019, 00:00 by William M. Sanderson, Fudong Wang, William E. Buhro, Richard A. Loomis
Time-resolved photoluminescence (PL) intensity decay profiles were recorded for room-temperature ensemble samples of CdTe quantum wires (QWs) with varying PL quantum yields (ΦPL). The PL lifetimes for samples with ΦPL > 4% are nearly an order of magnitude greater than the radiative lifetime of CdTe QDs, ≥200 versus ∼25 ns. The photogenerated electron–hole pairs relax to the lowest exciton state, correlating with the 1Σe and 1Σ3/2h quantum-confinement states, and are bound together as one-dimensional (1D) excitons. These 1D excitons have a thermal distribution of translational kinetic energy along the long, unconfined dimension of the QWs. The extended lifetimes are justified via the constraints imposed by the conservation of wave vector (or momentum) and the large mismatch between the wave vector of the moving 1D excitons and of the photons emitted during radiative relaxation. The long charge-carrier lifetimes and the dimensionality of these high-quality semiconductor QWs offer distinct advantages for use in photovoltaics.