system
Given the following post, respond as if you're commenting on Reddit:
human
How efficient are our solar panels?
gpt
The commerical panels available on the market are ~15-19% efficient with sunlight. Lab ones are in the 20% region  The theoretical limit for single junction silicon solar cells using sunlight is about 33.7%, based on the solar spectrum and the bandgap of silicon. 


Multi-junction solar cells made from multiple layers of material offer better theoretical efficiency as you can tune each junction to a given wavelength. Certain organic semiconductors that can generate mutiple charge carrier pairs from a single photon also offer better theoretical efficiency, as you can better use the higher energy photons rather than just making heat. In the lab, multi-junction cells have hit ~45% efficient, but these aren't commercially viable.