of the more important issues relating to the application of II-VI materials to photovoltaics. In fact it is comparatively recently that II-VIs started to become a commercial success in the PV market. Today, the copper-indium-(gallium)-selenide (CuIn(Ga)Se 2 , known as 'CIS' or 'CIGS') family of materials occupies a useful niche in the scheme of things, but still represents only a few percent of the total market. Incidentally, the CIS family itself will be covered in a future issue, whereas this article is mainly about the other mentioned chalcogenide II-VI materials, most notably the tellurides.
Collaborative developments
In wider terms the II-VI materials have been well known, of course, for their use in optoelectronics, notably in electroluminescent displays and detectors. A decade ago they were considered the best prospect for violet laser diodes. Since then, however, while work has continued it has tended to be fragmented. Numerous research activities are under way around the world, and a surprising proportion of this involves photovoltaics. There do not appear to be many concerted international programs for what looks to be a promising area for PV devices.
However, one such is the new European Supergen initiative, one of whose main research themes is PV devices, materials and technology, including research institutes with experience in II-VIs. The main thrust of this work is to deposit thin films of CdTe and CdS onto conducting oxide coated glass substrates. Sustainable Power Generation and Supply (Supergen) is a large, collaborative program of research based on an assembly of research consortia which will tackle the major challenges of sustainable power generation and supply. The UK government has earmarked Β£25 million (US$42 million) in funding for the initiative over a five-year program.* *F Fo or r m mo or re e o on n S Su up pe er rg ge en n, , g go o t to o: : www.epsrc.ac.uk/ website/default.aspx?ZoneID=3&MenuID=1615 **F Fo or r m mo or re e i in nf fo or rm ma at ti io on n o on n t th he e u us se e o of f c ca ad dm mi iu um m i in n P PV V, , d do ow wn nl lo oa ad d ' 'C Ca ad dm mi iu um m F Fa ac ct ts s a an nd d H Ha an nd dy y C Co om mp pa ar ri is so on ns s' ' f fr ro om m: : www.nrel.gov/cdte/pdfs/ cdte_factsheet.pdf