We review work on In2O3:Sn films prepared by reactive e‐beam evaporation of In2O3 with up to 9 mol % SnO2 onto heated glass. These films have excellent spectrally selective properties when the deposition rate is ∼0.2 nm/s, the substrate temperature is ≳150 °C, and the oxygen pressure is ∼5×10−4 Torr. Optimized coatings have crystallite dimensions ≳50 nm and a C‐type rare‐earth oxide structure. We cover electromagnetic properties as recorded by spectrophotometry in the 0.2–50‐μm range, by X‐band microwave reflectance, and by dc electrical measurements. Hall‐effect data are included. An increase of the Sn content is shown to have several important effects: the semiconductor band gap is shifted towards the ultraviolet, the luminous transmittance remains high, the infrared reflectance increases to a high value beyond a certain wavelength which shifts towards the visible, phonon‐induced infrared absorption bands vanish, the microwave reflectance goes up, and the dc resisitivity drops to ∼2×10−4 Ω cm. The corre...

Evaporated Sn‐doped In2O3 films: Basic optical properties and applications to energy‐efficient windows

This review provides numerical and graphical information about many (but by no means all) of the physical and electronic properties of GaAs that are useful to those engaged in experimental research and development on this material. The emphasis is on properties of GaAs itself, and the host of effects associated with the presence of specific impurities and defects is excluded from coverage. The geometry of the sphalerite lattice and of the first Brillouin zone of reciprocal space are used to pave the way for material concerning elastic moduli, speeds of sound, and phonon dispersion curves. A section on thermal properties includes material on the phase diagram and liquidus curve, thermal expansion coefficient as a function of temperature, specific heat and equivalent Debye temperature behavior, and thermal conduction. The discussion of optical properties focusses on dispersion of the dielectric constant from low frequencies [κ0(300)=12.85] through the reststrahlen range to the intrinsic edge, and on the ass...

Semiconducting and other major properties of gallium arsenide

Solar cells based on organometallic halide perovskite absorber layers are emerging as a high-performance photovoltaic technology. Using highly sensitive photothermal deflection and photocurrent spectroscopy, we measure the absorption spectrum of CH3NH3PbI3 perovskite thin films at room temperature. We find a high absorption coefficient with particularly sharp onset. Below the bandgap, the absorption is exponential over more than four decades with an Urbach energy as small as 15 meV, which suggests a well-ordered microstructure. No deep states are found down to the detection limit of ∼1 cm–1. These results confirm the excellent electronic properties of perovskite thin films, enabling the very high open-circuit voltages reported for perovskite solar cells. Following intentional moisture ingress, we find that the absorption at photon energies below 2.4 eV is strongly reduced, pointing to a compositional change of the material.

Organometallic Halide Perovskites: Sharp Optical Absorption Edge and Its Relation to Photovoltaic Performance

Transparent conductors as solar energy materials: A panoramic review

Electrochromic tungsten oxide films: Review of progress 1993–1998

The Long-Wavelength Edge of Photographic Sensitivity and of the Electronic Absorption of Solids

The absorption spectra of pure silver bromide and silver chloride crystals grown from the melt have been measured in and near the so-called "absorption edge," where the absorption coefficient increases very rapidly with frequency. The temperature-dependence of the absorption edge has also been investigated. More limited data have been collected on the absorption spectra of mixed AgBr---AgCl and AgBr---AgI crystals.

Optical Absorption of Pure Silver Halides

Crystals of simple and mixed silver halides are known to show a strong fluorescence but little afterglow at low temperatures. However, the slow buildup of luminescence under weak excitation indicates the presence of effective trapping processes. These processes have been studied in more detail on silver bromoiodide crystals. The lifetimes of the trapping states were estimated by observing the dependence of buildup rates on the dark interval between two exposures. The trapping states are also revealed by the effects of infrared radiation. If applied during excitation, it reduces the stationary brightness; if it is applied in the interval between exposures, it reduces the rate of re-excitation. The pattern of behavior of these phosphors is interpreted by a model of the type generally used in the description of zinc sulfide and similar photoconducting phosphors. If the absence of afterglow is taken into account, the model requires that the efficiency of the phosphor should increase with the square root of the exciting intensity. This has been confirmed experimentally over a range of 3 powers of 10. An afterglow can be produced in the silver bromoiodide by incorporating certain divalent cations (such as ${\mathrm{Cd}}^{++}$ or ${\mathrm{Sr}}^{++}$) into the crystal. From an extension of the model to this more complex system, a number of emission and stimulation effects can be deduced which have been found in a series of qualitative observations.

Franz Urbach

Papers

The Long-Wavelength Edge of Photographic Sensitivity and of the Electronic Absorption of Solids

Optical Absorption of Pure Silver Halides

Luminescence of Silver Bromoiodide Crystals

Method for determining image sharpness