This work presents a detailed exposition of a diagnostic method for subcell characterization in multi-junction solar cells (MJSCs) based on absolute electroluminescence (EL) measurements. A comprehensive measurement and modeling framework is established: absolute EL spectra are acquired using an integrating-sphere system, and by incorporating the reciprocity theorem and the luminescent-coupling model, quantitative conversion from measurable spectra to dark/illuminated J-V curves of each subcell is achieved. The method is successfully applied to a comparative analysis of InGaP/GaAs/InGaAs triple-junction solar cells (with and without MQWs), systematically revealing the external/internal radiative efficiencies, dark/light J-V curves, and power gains/losses for each subcell under both AM1.5G and AM0. The obtained results show high consistency with experimental J-V curves, with overall open-circuit voltage deviations of only 4–40 mV and overall conversion-efficiency deviations of merely 0.11–0.32% absolute. Furthermore, optimization strategies integrating subcell materials, structural parameters, and process factors (under both AM0 and AM1.5G spectra) are proposed, providing a reliable diagnostic tool and theoretical guidance for further design and fabrication. Consequently, this method is considered as a potential standard approach for quantifying subcell characteristics during MJSC manufacturing or for calibrating standard chips. • Detailed description for integrating-sphere based absolute EL measurement. • Complete formulas from absolute EL spectra to dark/light subcell J-V curves. • A comparative characteristics diagnosis on two IMM-3JSCs (w/and w/o MQWs). • Propose optimization strategies for further device design and fabrication.
Liu et al. (Fri,) studied this question.
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