A solar cell can never convert more than about a third of sunlight to electricity
The old claim turned out to be wrong and was rejected by evidence.
TaughtThere is a fundamental physics limit (the Shockley-Queisser limit, about 33.7%) on how much sunlight a single-junction solar cell can turn into electricity. Real silicon panels top out around 27%, and the theoretical ceiling of roughly one-third is a wall you cannot climb over.
NowIn November 2023, LONGi's crystalline-silicon/perovskite tandem cell was certified at 33.9% efficiency by the U.S. National Renewable Energy Laboratory, the first time a solar cell exceeded the 33.7% single-junction Shockley-Queisser limit.
What actually happened
The wall is real; the trick is that it only applies to a single-junction cell. Shockley and Queisser's 1961 limit assumes one light-absorbing layer, which must compromise: it wastes low-energy photons it can't absorb and squanders the excess energy of high-energy ones as heat.
A tandem stacks a perovskite layer tuned for high-energy light on top of a silicon layer tuned for the rest, so each photon meets a layer sized for it. That sidesteps the single-junction assumption entirely; the theoretical ceiling for this two-layer design is around 43%. The record has since climbed past 34% and beyond. What was disproved is the popular shorthand that 'a third is the hard limit for solar cells'; the honest version is that it was always the limit for one particular architecture.
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Who was taught this
Still standard through 2023, so anyone who finished school between 1950 and 2023 learned the earlier version.