Sounds very "translationese", I know. But let's start with this definition:

Laminato PV Modulo PV senza cornice, risultato dell’incapsulamento. Si presenta sotto forma di sandwich vetro-vetro, vetro-PVF oppure di un vetro isolante.
http://www.bipv.ch/glossario-pv-it.pdf

I think by default solar panels are glass-something else (i.e. the front layer is normally glass and the back layer is, say, polyvinyl fluoride) or it isn't an issue, so the "glass-glass" component doesn't come up so often. But it certainly exists - here it is on the International Energy Agency website:

Glass-glass laminates are generally at least 10 mm thick.
http://www.iea-pvps.org/pv/modules.htm

I don't think transparency has much to do with it, since the glass used is generally transparent - how transparent a module is seems to depend on the spacing between the cells.

A final note on module/panel. Some sites suggest they are synonymous, but the module appears to be smaller and a panel can be composed of one or more modules - see the IEA definitions:
http://www.iea-pvps.org/pv/glossary.htm

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Note added at 1 hr (2010-01-07 13:55:24 GMT)
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sorry, i guess my answer should have been in the plural...

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Note added at 4 days (2010-01-12 10:49:38 GMT) Post-grading
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Glad to be of assistance :-)