Solar electricity will never be economical, even if the cells are free and operate at maximum efficiency.
First free cells wouldnâ(TM)t be free. It would still cost thousands of dollars to put them up on a roof. We put a new asphalt shingle roof on our house (a nice suburban house not Algore mansion sized) a few years ago. It cost about $15,000.
I canâ(TM)t conceive of a generating material that would be as cheap as asphalt roofing, which is about as generic and low tech as it gets.
Furthermore the roofing business labor pool is also generic and low tech. Getting licensed electricians involved will only drive up labor costs.
I have not even noodled the price of wiring and the electronics needed to make the low voltage DC output of the cells usable.
Frames and land would be large costs for non-roof systems. Paving material? Around here roads are repaved every few years â" more cost.
Second, solar systems do not operate at night and their output can drop between 50 and 75% on a cloudy day. Every day has a night, and a majority of days around my location are cloudy. There are no economically viable systems for storing large quantities of electricity, therefor every watt of solar you are relying on must be backed up by a watt of something else. These days that is usually natural gas generation. This doubles the capital cost of solar systems.
Third, north of the tropics there is an annual variation in the amount of available solar energy. In my location at 40 north, the ratio between available solar energy in June and the amount in December is about 2.67 to 1. The amount of electricity used does not vary nearly that much. Electricity used for air conditioning in the summer is used for lighting, heating, and cooking in December. We often hear brownout alerts on the coldest days of the winter.
The implication of this is that two thirds of a solar electricity system big enough to supply us in December would sit idle in June, producing no revenue but still carrying a capital cost.
The punch line is that solar electricity is and will remain unaffordable no matter what the solar cell technology is.