Solar cell efficiency usually falls between 12.5-15 % and describes how much solar energy is actually converted into solar power in relation to the solar insolation that reaches the cell.
In laboratories, scientists are working on solar cell efficiency constantly. While best results for traditional solar cells lie around 22%, multi-junction cells have reached a solar cell efficiency of 42%. Commercial tandem cells are already available at 30% in real sunlight and up to 40% under concentrated sunlight. Solar cells made of crystalline silicon are now approaching the theoretical limiting solar cell efficiency of 29%.
Increasing solar cell efficiency has its effect on the price though. Highly efficient solar cells are often too expensive for commercial production and are mainly used for scientific purposes.
Solar cell efficiency can be broken down into several parameters like reflectance efficiency, thermodynamic efficiency, charge carrier separation efficiency and conductive efficiency. These aspects add up to the overall solar cell efficiency.
It is difficult to measure some of the solar cell efficiency parameters directly. So other parameters, that provide the necessary information, are measured instead. To calculate reflectance losses, the quantum efficiency is measured, for example. Other parameters that help determine solar cell efficiency are thermodynamic efficiency, quantum efficiency, VOC ratio, and fill factor.