How efficient are modern solar panels, and what's their limit?

The answer

Commercial silicon solar panels typically convert 20–24% of sunlight into electricity, while the theoretical maximum for single-junction silicon cells (the Shockley-Queisser limit) is about 33.7%. Multi-junction cells used in space applications have achieved over 47% efficiency in lab conditions by stacking layers that capture different wavelengths of light. Perovskite solar cells, a promising emerging technology, are cheaper to manufacture and have reached 33.7% efficiency in tandem with silicon - approaching the point where solar becomes the cheapest energy source in history.