Revealing Sub-Cell Degradation of Multi-Junction Solar Cells by Absolute Electroluminescence Imaging

Photovoltaic solar cells degrade or even fail during long-term storage, affecting their conversion efficiency and lifetime. In this work, an industry-standard InGaP/GaAs/InGaAs multi-junction solar cell (MJSC) was monitoredin a non-working idle state for more than two years. The sub-cell degradation caused by prolonged storage and its origin have been revealed by using the absolute electroluminescence (EL) imaging technique. Several potential defects were found to gradually exacerbate over time, introducing more non-radiative recombination centers and reducing the sub-cell external radiative efficiency under low-injection conditions. Quantitative evaluation results show that long-term idle resultedin an over 0.2% efficiency degradation and an over 1% fill factor degradation for each sub-cell, which is mainly originated from the non-radiative recombination loss.