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The aim of this research was to fabricate zinc oxide/cuprous(I) oxide-based heterojunction solar cells with the use of electrodeposition methods, and further to investigate their structures and photovoltaic properties. The ZnO and Cu2O were used as n-and p-type semiconductors, respectively, to fabricate photovoltaic devices based on Ag/ZnO/Cu2O/Cu(100) heterojunction structures. The crystallite sizes of ZnO and Cu2O were determined to be 25.4(3) nm and 69.8(6) nm, respectively. It was pointed out that efficiencies of the solar cells can be gradually adjusted, using different thicknesses of Cu2O layers, to achieve values as high as 2.7%. The standard diode model and high device performance provide new insights into the issue, outlining guidelines for high-performance solar cells and suggesting that a metal-n-type semiconductor-p-type semiconductor nanostructure-crystal layered, sandwiched-type architecture is a promising platform to boost the efficiency.

Abstract:The phosphor powders of Ca (m/2)−x Eu x Si 12−(m+n) Al m+n O n N 16−n (m = 1.6, n = 0.8, x in the range of 0-0.08) were synthesized by means of a solid state reaction in flowing nitrogen in a carbon resistant furnace and the influence of Eu concentration on the crystal structure and photoluminescent properties was thoroughly studied. The optical properties of selected α-sialon:Eu 2+ samples at temperatures in the range of 10 to 500 K and pressures up to 240 kbar are presented. The crystal lattice parameters were affected by doping with europium and some increase of the unit cell volume was observed up to 6 mol % of Eu. The higher concentration of europium led to subtle changes in the overall structure of the produced sialon phosphors. It was shown that the chemical composition of Ca, Eu-α-sialon phosphor was slightly different from the designed one and the phosphor powders were contaminated by AlN. The phosphor particle surface showed significant europium and oxygen enrichment with Eu 3+ but below the thin surface layer Eu 2+ was dominant and higher nitrogen content was observed. After examination of absorption, excitation, and emission spectra it was found that the emission peak position shifted toward longer wavelengths with rising Eu 2+ concentration from 565 nm (0.1 mol % Eu 2+ ) to 585 nm (10 mol % Eu 2+ ). The quantum yield of the phosphors reached the maximum at a rather low concentration of 4 mol % of Eu. Excitation spectra depend on the monitored wavelength which is typical for multisite Eu 2+ . The existence of many Eu 2+ sites in the sample was supported by the dependence of the decay time on the monitored wavelength.

Cuprous (I) oxide (Cu2O)-based solar cells were fabricated with the use of the electrodeposition technique at nanometre-scale, and the structural, morphological and electrical properties were investigated. The Cu2O layers were electrodeposited on crystalline and polycrystalline copper substrates. To complete the Cu2O/Cu(100) and Cu2O/Cu interfaces as the solar cells the top electrodes of silver paste were painted on the rear of Cu2O. The microscopic analysis exhibits uneven surface morphologies of a Cu2O film with the roughness of 92.5 nm, while the X-ray diffraction analysis reveals that the layers are Cu2O-type polycrystalline structures with the thickness of 493 nm and the crystallite size of 69.8(6) nm. The theoretical analysis of the current-voltage curve was provided to determine the values of electrical parameters of the most efficient solar cell of Ag/Cu2O/Cu(100) and clearly indicate presence of two Schottky barriers at interfaces.