Molten Salt Electrolytes for Electrodeposition of CdTe Films

We report preliminary investigation of several molten salt electrolytes containing CdCl2 and TeCl4 for the electrodeposition of CdTe films at temperatures well above (\u3e250 °C) those used with aqueous and organic electrolytes. These high temperatures have potential todramatically increase the crystallite size (Poole, Engelken, et al., 1994), as is important for optoelectronic device applications of CdTe, a leading II-VIsemiconductor. This paper willsurvey the results obtained withelectrolytes such as B2O,/HBO2 (m.p. - 230\u27C), NaCH3COO (m.p. » 324°C), ZnCl2 (m.p. - 283*C), and LiCl/KCl (m.p. * 350 °C), with an emphasis on the latter two. Key material to be presented includes 1) voltammetric data for the solutions, 2) x-ray diffractometry data for deposited films, 3) a discussion of the numerous practical problems associated withhigh temperature electrochemistry, especially incorrosive, volatile systems, and 4) emphasis of the value of an operationally feasible high temperature plating system to the commercial viabilityof electrodeposited semiconductor films

Electrodeposition of Copper Indium Sulfide Films from Organic Solutions

We report on organic solutions ofCuCl 2 ,InClg, and elemental sulfur for electrodepositing CuIn x Sv films. CuInS 2 and CuInSe 2 are promising solar cellmaterials; our work on CuInSg prefaces planned work on plating CuInSe 2 from nonaqueous solvents. Two promising solvent systems are (1) mixed propylcne carbonate and water and (2) mixed ethylene glycol, propionic acid, and water (Engelken et al., 1988). Gray-brown films ofCuInx Sy (nominally GuInS2 ) have been plated from both baths. Major problems include (1) reduction ofCu+2 to Cu and Cu x S by the solvent at high temperatures (T\u3el()0°C), hence depleting Cu+2,(2) poor adherence/uniformity, (3) controlling stoichiometry, and (4) sluggish indium deposition. The paper willdiscuss our routes to solving these problems and present filmdata

Improved Methods for Electroplating Cadmium Sulfide Thin Films

We report improved methods for electroplating cadmium sulfide (CMS) films. Aprevious problem was cracking/flaking of films deposited from organic solutions of elemental sulfur; attempts to improve adhesion via bath additives reduced grain size. Aqueous baths of thiosulfate ions yield cadmium-richness at low T temperatures (T), long deposition times, and/or poor bath stability. Developments in our work to be discussed include (1) plating ofuniform, adherent, and stoichiometric CdS from tetraethylene baths of CdCl 2 and elemental sulfur at T \u3e70° C with minimal cracking/flaking, (2) improved uniformity/ adherence by use of CdL\u3e, and (3) swept voltage methods in aqueous thiosulfate baths to plate stoichiometric (vs. Cd-rich) films near room temperature

Preparation of Powder Precursors and Evaporation of Photoconductive Indium Sulfide Films

We have demonstrated significant photoconductance in indium sulfide thin films prepared by thermal vacuum evaporation ofIn2$3 powders synthesized in-house by chemical precipitation ofInCl3 or In(CH3COO)3, and (NH4)2S or Na2S. The Delta G lambda/Gdark values have been as high as 0.1 in the initial unoptimized films. Excess sulfur (via a mixture of polysulfide and sulfide ions in the synthesis bath) appears to be important in achieving reproducible and large photoconductivities. In2S3 is particularly attractive as a lower toxicity alternative to CdS in optoelectronic applications such as photovoltaic and photoconductive cells

Reaction of Titanocene Dichloride with Acetylenedicarboxylate

The reaction of Cp2TiCl2 with either the mono- or dipotassium salt of acetylenedicarboxylic acid (ADC) gives high yields of an insoluble orange product. The insoluble compound shows potential semiconductor behavior, as evidenced by an apparent bandgap in the orange region of the visible spectrum. Under N2 ,the compound decomposes at 238° C, eventually losing approximately 46% total mass up to 1350° C. The exothermic decomposition in air, beginning at 235° C, results in the formation of titanium oxides

Amorphous Silicon Solar Cells: A Review

Recent developments in the production and study of the properties of amorphous silicon containing hydrogen and fluorine impurities are reviewed. Especially emphasized are the properties of the material in regard to its photovoltaic potential and the roles of hydrogen and fluorine in modifying such properties as band gap and mobility from those of the pure amorphous and crystalline material