Indium selenide films

Antimony telluride films have been grown from antimony(III) and tellurium(IV) oxides.167 Antimony telluride films were stoichimetric and consisted of nanoscale particles of the size 100 nm. The films had a good crystallinity.167 Indium selenide films were grown from indium sulphate and selenium oxide precursors.168 The films consisted of large particles, 70 to 200 nm in diameter. The band gap was 1.73 eV.168... 

X-ray diffraction patterns of the films showed peaks characteristic of the chalcopyrite copper indium selenide or copper indium telluride compounds. Auger spectra and depth profiles showed the expected signal plus some carbon and surface oxidation. The stoichiometry varied with depth. 

A heterojunction of copper indium selenide on n-type cadmium sulfide indicated that the films, as deposited, were p-type. These films yielded an OCV of 100 mV and SCC of 2 mA/cm . The main problem with these films was poor grain morphology. 

Semiconductor deposition materials used include amorphous silicon, polycrystalline silicon, micro-crystalline silicon, cadmium telluride, and copper indium selenide/sulfide. Typically, the top surface is low iron solar glass for rigid cells (a fluoropolymer for flexible cells), the encapsulant is crosslinkable ethylene-vinyl acetate (EVA), and the rear layer is a Tedlar - PET - Tedlar laminate (although glass, coated PET, or another bondable polymeric film are also used). 

Cachet H, Cortes R, Eroment M, Mamin G (1997) Epitaxial electrodeposition of cadmium selenide thin films on indium phosphide single crystal. J Solid State Electrochem 1 100-107... 

There are three main thin-film PV cells under development at present amorphous Si, CdTe/CdS, and Cl(G)S/CdS [C1(G)S refers to copper indium (gallium) selenide]. Of these, the last two are polycrystalline (as opposed to amorphous), and both normally employ CD CdS. Crystalline Si cells are not thin films, being at least tens and usually hundreds of microns in thickness, compared to the few microns of active thickness of the thin-fihn cells. 

Another area of development is in lower-cost thin- and ultrathin-film designs. One such product is made by Nanosolar of copper indium gallium selenide (CIGS), which is claimed to achieve up to 19.5% efficiency and is as thin as a newspaper. This claim is yet to be proved. The collector cost is also reduced, because the substrate material on which the ink is printed is much less expensive than the stainless steel substrates that are often used in thin-film solar panels. The manufacturer claims a five- to tenfold reduction in the collector cost (about 1/W) compared to conventional PV cells. 

The approach to HTSC electrosynthesis described in this section is entirely analogous to that used for the production of semiconductive films such as CujcInj,S(Se)j [205,206]. The thermal treatment of electrodeposited metallic precursors carried out in an H2S(Se) atmosphere in some cases proved more successful than the cathodic codeposition of sulfur or selenium with the metals [207]. There is also an analogy with other combined methods of selenide preparation the sputtering of copper or indium followed by cathodic deposition of selenium [208], and the chemical reaction of selenium with metals. In this case, as in the deposition of incomplete HTSC precursors [189], the use of the deposition mode is much easier. 

The thin-film materials that are discussed in this chapter can be used in depositing one or more thin layers of material on a substrate in the following PV cell technologies (i) CdTe, (ii) copper indium (galUum) selenide (CIS or CIGS), and (iii) Dye-sensitized solar cell (DSSC). The thickness of such layers can vary from a few nanometers to tens of micrometers. 

Substrates, Films are usually prepared on platinum or gold electrodes which are inert, but semiconducting materials including indium tin oxide, n-type polycrystalline silicon, gallium arsenide, cadmium sulphide and cadmium selenide, graphite [38, 59], and oxide covered metals [60] have also been used. In the majority of cases, the films are produced readily and the only serious limitations are the potential and the nucleophilic nature of the solution. 

Apart from metals, good-quality polypyrrole films have also been prepared using a variety of semiconducting materials, such as indium-tin oxide (ITO) glass [39,40], gallium phosphide [41], silicon [42-44], cadmium sulfide, or cadmium selenide [45] as the electrode. 

---