Characterization of multiterminal tandem photovoltaic devices and their subcell coupling

Three-terminal (3T) and four-terminal (4T) tandem photovoltaic (PV) devices using various materials have been increasingly reported in the literature, but measurement standards are lacking. Here, multiterminal measured as functions of two load variables characterized unambiguously three device voltages or currents on hexagonal plots. We demonstrate these techniques GaInP/GaAs solar cells, with a middle contact between subcells, example 3T both series-connected reverse-connected subcells. Coupling mechanisms subcells quantified within context simple equivalent optoelectronic circuit. Electrical optical coupling most clearly revealed coupled dark measurements. These measurements sensitive enough to observe very small luminescent from bottom subcell top prototype device. Quick simplified also discussed complete characterization.