Quantitative determination of luminescent coupling in multijunction solar cells from spectral photovoltage measurements

We present a simple method to quantify the magnitude of luminescent coupling (LC) between stacked subcells in multijunction photovoltaic devices. The effect of luminescence produced at high-band-gap subcells on underlying low-gap units within the same device can be directly accessed as a measurable open-circuit voltage difference by comparing two photovoltage spectra. Additionally, our study unambiguously identifies LC as the modulation mechanism across multijunction solar cells generating a response from buried subcells in photoreflectance measurements