Films For Solar Applications Research Articles

Effects of HCl and Methanol in the Precursor on Physical Properties of Spray-Deposited Nanostructured CuO Thin Films for Solar Applications

The influence of the presence of HCl and methanol in the precursor on CuO absorber layers deposited by spray pyrolysis has been investigated. The films were deposited on glass substrate at fixed substrate temperature of 450°C using 0.05 molar CuCl2·2H2O in deionized water containing a specific amount of HCl and methanol. The structural, morphological, electrical, and optical properties of the resulting thin films were studied to evaluate their suitability for solar applications. Presence of HCl increased the concentration of Cu2+ ions in the precursor, leading to a rise in the Cu concentration in the resulting film, which improved the crystallinity with increased mean grain size, surface roughness, and carrier mobility at the cost of decreased carrier concentration. However, film deposited with excess HCl suffered from corrosion and huge cracks, making it unfavorable for solar applications. On the other hand, although presence of methanol improved the crystallinity of the resulting film, the surface was smooth due to lower deposition rate. Kubelka–Munk theory was used to estimate the optical bandgap of the deposited thin films, revealing values fairly close to optimum for solar cell applications.

Optimization of the Electrodeposition Parameters to Improve the Stoichiometry of In2S3 Films for Solar Applications Using the Taguchi Method

Properties of electrodeposited semiconductor thin films are dependent upon the electrolyte composition, plating time, and temperature as well as the current density and the nature of the substrate. In this study, the influence of the electrodeposition parameters such as deposition voltage, deposition time, composition of solution, and deposition temperature upon the properties of In2S3 films was analyzed by the Taguchi Method. According to Taguchi analysis, the interaction between deposition voltage and deposition time was significant. Deposition voltage had the largest impact upon the stoichiometry of In2S3 films and deposition temperature had the least impact. The stoichiometric ratios between sulfur and indium (S/In: 3/2) obtained from experiments performed with optimized electrodeposition parameters were in agreement with predicted values from the Taguchi Method. The experiments were carried out according to Taguchi orthogonal array L27 (3∧4) design of experiments (DOE). Approximately 600 nm thick In2S3 films were electrodeposited from an organic bath (ethylene glycol‐based) containing indium chloride (InCl3), sodium chloride (NaCl), and sodium thiosulfate (Na2S2O3·5H2O), the latter used as an additional sulfur source along with elemental sulfur (S). An X‐ray diffractometer (XRD), energy dispersive X‐ray spectroscopy (EDS) unit, and scanning electron microscope (SEM) were, respectively, used to analyze the phases, elemental composition, and morphology of the electrodeposited In2S3 films.

Structure-Infrared Optical Property-Correlations of C,O,H-Polymers for Transparent Insulation and Greenhouse Applications

In this paper an understanding of the physical relationships between the material structure and the temperature dependent infrared optical properties of different transparent polymer films for solar applications is described. The infrared optical properties are relevant for the heat transport of e.g. greenhouse and transparent insulation structures. The properties were determined based on infrared transmittance measurements and the assumption of a constant index of refraction from the visible range. To establish structure-property-correlations molecular structure parameters such as the concentration of carbon-oxygen single bonds and carbon-hydroxyl groups were determined. For 50 μm thick films a good correlation between the concentration of the functional carbon-hydroxyl and the carbon-oxygen group and the infrared optical thickness as well as the hemispherical emittance was found. This correlation fits well for high and low infrared radiation absorbing polymeric materials consisting of carbon, hydrogen, and oxygen atoms. The carbon-hydroxyl group appears to be slightly more effective than the carbon-oxygen single bond. Interestingly, the correlation works for polymers with aromatic (PC, PET) and aliphatic (PMMA, CTA, ethylene copolymers) groups.

Structure–infrared optical property-correlations of polar ethylene copolymer films for solar applications

Abstract In this paper, an understanding of the physical relationships between the material structure and the infrared optical properties of polar ethylene homo and copolymers for solar applications is described. The infrared optical properties are relevant for the heat transport of transparent insulation structures based on these materials. To establish structure–property-correlations molecular structure parameters such as comonomer content and the concentration of carbon–oxygen single bond and carbon–hydroxyl groups, respectively, were determined. For 50 μm thick films a good correlation between the concentration of the functional carbon–hydroxyl and the carbon–oxygen group and the infrared optical thickness as well as the hemispherical emittance was found. The carbon–hydroxyl group appears to be slightly more effective than the carbon–oxygen single bond.

High efficiency CuInSe2–(CdZn)S solar cells: fabrication, results, and analysis

The CuInSe2 thin films for solar application are grown by physical vapor deposition in a standard evaporation system. Indium-doped high conductivity (CdZn)S is evaporated onto the CuInSe2 to form the junction. The CuInSe2–(CdZn)S devices require air heat treatments to achieve the highest efficiency. High-efficiency small-area devices exceeding 11% (87.5 mW/cm2, ELH, T = 32 °C) have been fabricated this way. The behavior of the devices cannot be described as a classical heterojunction dominated by interface recombination. Instead, current–voltage and spectral-response analysis show that the diode current transport is dominated by a Shockley–Read type of recombination model, with space–charge being the dominant recombination mechanism via midgap states, with an estimated concentration of 1014 cm−3.