The effect of luminescent coupling on modulated photocurrent measurements in multijunction solar cells

Abstract

Luminescent coupling in multijunction solar cells has a major impact on device response, and its impact on current-voltage and quantum efficiency measurements is well established. However, the role of luminescent coupling in more advanced characterization techniques such as modulated photocurrent spectroscopy is virtually unknown. Here we present measurements of the frequencydependent photocurrent of a triple junction solar cell with significant coupling between adjacent junctions. We develop an equivalent circuit model that includes luminescent coupling which shows good agreement with the measured frequency response. The model also shows how the system response can elucidate the type of charge carrier recombination in these III-V semiconductor materials.

What Limits the Voltage of GaAs Photovoltaic Devices under Low Indoor Light?

“…The dependence of the ERE on injection level, whether by electron injection (EL) or photon excitation (PL), in GaAs-based structures and devices, has been studied in the past and a similar outcome to our finding here has been reported. [25,[34][35][36] The ERE is often described as the product of the internal radiative efficiency (IRE) and the extraction efficiency η, with the former being defined as the ratio of the net generated photons in the active layer to the total carriers injected there. Therefore, the improvement of the ERE with injection is a consequence of the IRE improvement with injection level as the extraction efficiency is generally injection independent.…”