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We report electroluminescence ͑EL͒ from 50 nm silicon oxynitride films on p-type crystalline silicon substrates in a Au/silicon oxynitride/Si structure. The EL intensity has a peak below 2.45 eV, and is consistent with radiative recombination of injected carriers. The EL is present only in annealed samples, and the emission is similar to the photoluminescence from the same samples. The current-voltage behavior is indicative of space charge-limited current. No polarity or field dependence of the EL peak energy is observed. This phenomenon is attributed to the relaxation of carriers down the band tails before recombination.

An inexpensive, combinatorial method to evaluate an array of metal oxide materials as photocatalysts for solar fuel production utilizing spray pyrolysis is presented. This new approach capitalizes on the inherent properties of spray pyrolysis. We take advantage of the natural lateral gradient produced in a spray cone to fashion four-metal-threeat-a-time compositional triangular patterns on conductive glass substrates from simple nitrate salt precursor solutions. Subsequent annealing produces thin-film electrodes that are readily screened for photochemical activity using a simple laser scanner system. The apparatus employed is constructed from readily available commercial components, making it accessible to a wide number of laboratories. Our method complements other combinatorial methods in that it provides a chemically different environment for the formation of materials that might produce different morphologies and metal oxidation states and it allows for easy evaluation of layered structures, as well single-phase materials, thereby expanding the number of unique materials tested as potential photocatalysts. As a proof of principle, the discovery and optimization of a new Na-doped CuBi 2 O 4 photocatalyst is described.

LaFe x Co (1– x ) O 3 thin films were prepared on fluorine-doped tin oxide conducting glass substrates by spray pyrolysis without any conductive additives and evaluated for their ability to catalyze the oxygen reduction reaction. Onset potential and current density were found to be comparable to platinum, and the resulting crystallite size was on the order of 20 nm. Coordination of the precursor metal ions by citrate was found not to be advantageous. Results from multiple scan linear sweep voltammetry suggest lattice oxide saturation during reduction of oxygen and lattice oxide depletion upon water oxidation. The color of the best-performing composition changes dramatically between 1.2 and −1.15 V versus saturated calomel electrode, so X-ray photoelectron spectra of the fully oxidized and reduced films were compared, demonstrating that cobalt in the film changes oxidation state. Performance of the films as a function of iron-to-cobalt ratio is consistent with what others have reported in the literature, indicating that spray pyrolysis is an efficient method to prepare and evaluate new catalytic materials.

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