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Various optical and electrical properties of the I-III-VI2 compounds CuGaS2 and CuInS2 have been studied. From the results of low-temperature luminescence and ref lectivity, both crystals are determined to have a direct band gap. The band gaps at 2'K are 2. 53 eV for CuGa82 and 1.55 eV for CuIn82. CuInS2 has been made conducting both n and. p type, vrhile CuGa82 has been made p type only. Electroreflectance measurements have been performed in an attempt to determine the band structure. The highest valence band appears to be a doublet rvith a 1Rrge admixture of Cu 3d %'Rve functions.

We report CuInSe2/CdS p-n heterojunction photovoltaic detectors which display uniform quantum efficiencies of up to ∼70% between 0.55 and 1.25 μ. Response times as short as 5 nsec have been observed. A weak electroluminescence (0.01% external quantum efficiency) peaking near 1.4 μ has also been observed at room temperature.

The oxidation state of iridium ions in an oxide film grown electrochemically on an Ir metal reflector electrode in aqueous 0.5M H2SO4 electrolyte can be rapidly and reversibly modulated by voltage pulses of 1 V amplitude according to the reaction: Ir(OH)n(transparent) ⇄IrOx(OH)n−x(colored)+xH++xe. This valency interconversion produces a marked change in light absorption throughout the visible wavelength region and occurs without change in film thickness. Color-bleach cycles exhibit reflectance contrast changes, ΔR/R, and charging times, τ, suitable for electrochromic display devices, e.g., for a film 700 Å thick: ΔR/R=60% at λ=546 nm and τ≈40 msec. The fast write-erase times are made possible by the highly porous and hydrated nature of the oxide film. The charge (∼20 mC cm−2) and energy (∼20 mJ cm−2) are comparable with those for other electrochromic oxide systems, e.g., the tungsten bronzes. Advantages of the iridium oxide system include: (i) fast response; (ii) stability of the colored written state in the presence of water and dissolved O2; (iii) broad spectral absorption; and (iv) the ability to grow and reform the oxide layer insitu in the electro-optic display cell. Electrochromic spectra of anodic iridium oxide films are illustrated and related to charge-transfer and intervalency transitions.

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The room-temperature electrical properties of ten I-III-VI2 (I=Cu, Ag; III=Al, Ga, In; VI=S, Se) compounds are presented. The resistivities of eight of these compounds are rapidly changed by annealing under maximum and minimum chalcogen pressures. The Cu compounds can readily be made p type, a feature lacking in the analogous II-VI compounds. However, the Cu compounds with energy gaps of 1.7 eV or above have not been made n type.

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