Multiple-junction solar cells

Main article: Multijunction solar cell

The record for multiple junction solar cells is disputed. Teams led by the University of Delaware, the Fraunhofer Institute for Solar Energy Systems, and NREL all claim the world record title at 42.8, 41.1, and 40.8%, respectively. Spectrolab also claims commercial availability of cells at nearly 42% efficiency in a triple junction design. NREL claims that the other implementations have not been put under standardized tests and, in the case of the University of Delaware project, represents only hypothetical efficiencies of a panel that has not been fully assembled. NREL claims it is one of only three laboratories in the world capable of conducting valid tests, although the Fraunhofer Institute is among those three facilities.