Methods for analysis of two-functional, two-terminal photovoltaic devices

Accurate measurement techniques are essential to the advancement of photovoltaic device technologies. Measurements of multijunction, two-terminal devices (Ga_0.5In_0.5As/GaAs solar cells) are especially difficult because researchers need to be able to characterize the individual cells but are unable to connect directly to them. We describe a single-source simulator (with large-area filters) method for obtaining current-voltage (I-V) curves of both the individual cells and the tandem cell for arbitrary spectra. The filters used for the I-V measurements and for quantum efficiency (QE) measurements are somewhat different. Voltage biasing for QE measurements is useful when one cell is shunted or has a small reverse breakdown voltage, but is often unnecessary for Ill-V devices