Yes the first out of laboratory cells were may be unable to pay back their enery a decade ago (and we're not even sure because we have no real lifetime data yet).

Wikipedia has many links to studies for payback time:

http://en.wikipedia.org/wiki/Photovoltaic_cells

The absolute worse we produce right now (or produced a few years ago) installed in a poor place has 5 years payback everything included (roof mounting, etc...). It's easy to get 1-2 year.

From what I understand from my readings the big thing to know is that the PV cell industry uses computer chip industry silicon and the computer chip industry couldn't care less about energy used during production since what they produce is worth way more than gold per kilogram on the market.

If/when the market for PV gets bigger, they'll move to silicon production dedicated to PV cells where energy input is likely to be way smaller and prices will go down big time too (since they won't compete with silicon-gold-chips for this ressource anymore).

The wikipedia timeline has many interesting information:

http://en.wikipedia.org/wiki/Timeline_of_solar_cells

# 1984 - 30,000 SF Building-Integrated Photovoltaic [BI-PV] Roof completed for the Intercultural Center of Georgetown University. At the time of the 20th Anniversary Journey by Horseback for Peace and Photovoltais in 2004 it was still generating an average of one MWh daily as it has for twenty years in the dense urban environment of Washington, DC.

Probably in the worst place (pollution, etc...) old technology PV are still working after 23 years.

# 1984 - Amoco Oil pulled factory loan to make brutal and unwelcome takeover of Solarex Corporation factory in Frederick, Maryland.
# 1988-1991 AMOCO/Enron used Solarex patents to sue ARCO Solar out of the business of a-Si, see Solarex Corp.(Enron/Amoco)v.Arco Solar, Inc.Ddel, 805 Fsupp 252 Fed Digest.

As with batteries and electric cars, intellectual property is used to gain a few decades of big oil profits and other pro global warning activities.

Section 8. The Congress shall have power [...] To promote the progress of science and useful arts, by securing for limited times to authors and inventors the exclusive right to their respective writings and discoveries;

Promote progress indeed.