In this work we have investigated the temperature-dependence of the band-edge photoluminescence decay of efficiently luminescing organically capped CdSe quantum dots ͑QDs͒ with diameters ranging from 1.7 to 6.3 nm over a broad temperature range ͑1.3-300 K͒. The overall trend is similar for all the investigated sizes, consisting of different temperature regimes. The low-temperature regime ͑below ϳ50 K͒ is characterized by purely radiative decay and can be modeled by a thermal distribution between a lower dark and a higher bright exciton state, with a size-dependent energy separation ͑viz., from 0.7 to 1.7 meV͒ and dark exciton lifetime ͑viz., from 0.3 to 1.4 s for QDs ranging from 6.3 nm to 1.7 nm in diameter͒. Nonradiative relaxation processes become increasingly important above ϳ50 K until the temperature antiquenching regime is reached, leading to a decrease in the nonradiative contributions and photoluminescence intensity recovery above ϳ200 K.

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The formation chemistry and growth dynamics of thin-film CuInSe2 grown by physical vapor deposition have been considered along the reaction path leading from the CuxSe:CuInSe2 two-phase region to single-phase CuInSe2. The (Cu2Se)β(CuInSe2)1−β (0<β≤1) mixed-phase precursor is created in a manner consistent with a liquid-phase assisted growth process. At substrate temperatures above 500 °C and in the presence of excess Se, the film structure is columnar through the film thickness with column diameters in the range of 2.0–5.0 μm. Films deposited on glass are described as highly oriented with nearly exclusive (112) crystalline orientation. CuInSe2:CuxSe phase separation is identified and occurs primarily normal to the substrate plane at free surfaces. Single-phase CuInSe2 is created by the conversion of the CuxSe into CuInSe2 upon exposure to In and Se activity. Noninterrupted columnar growth continues at substrate temperatures above 500 °C. The addition of In in excess of that required for conversion produces an In-rich near-surface region with a CuIn3Se5 surface chemistry. A model is developed that describes the growth process. The model provides a vision for the production of thin-film CuInSe2 in industrial scale systems. Photovoltaic devices incorporating Ga with total-area efficiencies of 14.4%–16.4% have been produced by this process and variations on this process.

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Epitaxial growth of the ordered vacancy compound CuIn3Se5 has been achieved on GaAs (100) by molecular beam epitaxy from Cu2Se and In2Se3 sources. Electron probe microanalysis and x-ray diffraction have confirmed the composition for the 1-3-5 phase and that the films are single-crystal CuIn3Se5 (100). Transmission electron microscopy characterization of the material also showed it to be single crystalline. Structural defects in the layer consisted mainly of stacking faults. Photoluminescence measurements performed at 7.5 K indicate that the band gap is 1.28 eV. Raman spectra reveal a strong polarized peak at 152 cm−1, which is believed to arise from the totally symmetric vibration of the Se atoms in the lattice.

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We report the first observation of band-gap energy reduction in Ga0.47In0.53As deposited on (100) InP by atmospheric pressure organometallic vapor phase epitaxy due to CuPt-type ordering. A reduction of more than 65 meV in the band-gap energy is observed for lattice-matched samples that show strong CuPt-like ordering by transmission electron microscopy. By comparison samples that show no CuPt-like ordering diffraction signatures, do not have reduced band-gap energies. Studies of the influence of growth parameters on the band-gap energy indicate a U-shaped dependence on the growth temperature with a minimum around 550 °C and decreasing band-gap energies with increasing growth rate (at a constant V/III ratio) over the range 0.5–4 μm/h.