I wouldn’t say it will always be a problem. Right now, the efficiency is in the teens and twenties. I think, when solar tech matures, we’ll get much higher efficiency numbers.
Not really. The reason why has to do with quantum physics. Each photon (quanta of light) has energy that is proportional to its frequency (hv with h being Planck’s constant and v being the frequency of that particular color of light). Sunlight has several ‘colors’ of light within it, therefore several different energies. Additionally each of these photons of different energies will yield a different voltage when converted to electricity. The last sentence is why it is not possible to go too much further in efficiencies. With a pair of wires, only one voltage can be generated. This means that photons with energies below the threshold (output voltage – barrier voltage) will be reflected or turned into heat. Photons with higher energies will convert to electricity but the energy above the conversion energy will be converted to heat.
There have been attempts to fix this with multi-layer, multi-tap solar cells, but these also have issues.
