Defect‐induced current coupling in multi‐junction solar cells revealed by absolute electroluminescence imaging

Abstract

AbstractAn electroluminescence (EL) anomaly singular spot was observed in an industry‐standard InGaP/GaAs multi‐junction solar cell (MJSC). Affected by this singular spot, the spatially resolved subcell current distributions were found to exhibit unique opposite characteristics, which we call “defect‐induced current coupling.” Herein, we conducted systematic investigations to reveal the defect‐induced current coupling phenomenon, for the first time, through the absolute EL imaging technique. Specifically, a modified carrier‐balance model was first proposed to describe the subcell optoelectronic distribution around the singular spot. Then, optical and electrical properties including subcell non‐radiative recombination distributions, J–V characteristics, essential photovoltaic parameters, and energy losses were quantitatively extracted for characterizing the performance inhomogeneity caused by the defect‐induced coupling. Moreover, a three‐dimensional distributed circuit model was established to numerically simulate the absolute EL emissions and extract local electrical parameters around the singular spot. Simulation results revealed that the defect‐induced current coupling phenomenon is attributed to the deterioration of weak‐diode and shunt parameters at the GaAs bottom cell, and the efficiency of the MJSC was estimated to be reduced by 0.408% compared with the defect‐free MJSC model.