People often ask me this question and I though it is best to explain it here once for all.
Most people think that Solar Panel is just Silicon Diodes, But well You have to understand the What a Solar Panel is made of
1) Silicon Diodes
2) Aluminum Frame
3) Glass Protective Layer
The of manufacturing Silicon Diodes is only 50% or less , The rest in the commodity metal like Aluminum, whose are pretty stable over the period of time.
Slicion Part of the Solar Panel is offcourse following the Moore’s law
But also the problem is with the efficiency of the Absorption co-efficients, most diodes in commercials panels are pretty in-efficient that means
Only 18 to 21 % of energy is absorbed and converted to electricity at STC, in the field they absorb abysmal <15%
These factors make per-watt cost of Solar Panel more expensive. If we just double the panel efficiency, then for same wattage 50% less aluminum, 50% less glass and 50% less silicon.
So the right Question would be instead on Why, How can we make Solar Panel less expensive.