A solar panel converts sunlight at a rate physicists drew a hard ceiling around in 1961, and the two-layer trick that just crossed that 65-year-old limit is now racing toward a factory floor near you

The 1961 equation that capped an entire industryEvery single-junction solar cell faces a fundamental ceiling known as the Shockley-Queisser limit, derived in 1961 by William Shockley and Hans-Joachim Queisser. That figure cleared the 33.7% Shockley-Queisser ceiling for single-junction cells by a wide margin. The architecture making this possible is the tandem solar cell, two semiconductor layers bonded into one device. Crystalline silicon-perovskite tandem solar cells carry a theoretical efficiency limit of 43%, far surpassing the Shockley-Queisser limit for single-junction cells. The US solar cell manufacturing base is still building toward the upstream steps this technology will eventually need.