摘要： Keeping track of the rapidly improving solar cell performance is not as easy as it might seem. Martin Green describes the Solar Cell Efficiency Tables that have been providing 6-monthly updates of record solar cell performance since the 1990s. Solar cells have become the lowest-cost source of electricity in many countries because their price has dropped dramatically, thanks partly to enhanced energy conversion efficiency, which has improved across all solar cell technologies. For single cells, the efficiency is fundamentally limited by the Shockley–Queisser (SQ) limit of 33.8%, with the well-established GaAs and Si cells the closest to this limit. Particularly rapid progress is evident for perovskite and organic cells. The SQ limit can be exceeded by stacking cells from different materials, each converting part of the solar spectrum. Such multi-junctions already surpassed the SQ limit experimentally in 2009. However, measuring efficiency is more difficult than it might appear, and by the 1980s the solar cell community was calling for the ‘independent confirmation’ of cell results by a recognized test centre. In the 1990s, I started compiling the Solar Cell Efficiency Tables, with the aim of providing an authoritative summary of the progress and encouraging independent confirmation of results — which was a necessary condition for inclusion in the Tables.