Visualizing localized, radiative defects in GaAs solar cells

• Published in: Scientific reports Vol. 12; no. 1; p. 14838
• Main Authors: Hamadani, Behrang H., Stevens, Margaret A., Conrad, Brianna, Lumb, Matthew P., Schmieder, Kenneth J.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-09-2022; Nature Publishing Group; Nature Portfolio
• Subjects: 639/4077/909/4101/4096/946; 639/624/399; Efficiency; Energy; Gallium; Humanities and Social Sciences; Lasers; Luminescence; multidisciplinary; Organic chemicals; Photons; Point defects; Recombination; Science; Science (multidisciplinary); Solar cells; Spectrum analysis
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-022-19187-4

We have used a calibrated, wide-field hyperspectral imaging instrument to obtain absolute spectrally and spatially resolved photoluminescence images in high growth-rate, rear-junction GaAs solar cells from 300 to 77 K. At the site of some localized defects scattered throughout the active layer, we report a novel, double-peak luminescence emission with maximum peak energies corresponding to both the main band-to-band transition and a band-to-impurity optical transition below the band gap energy. Temperature-dependent imaging reveals that the evolution of the peak intensity and energy agrees well with a model of free-to-bound recombination with a deep impurity center, likely a gallium antisite defect. We also analyzed the temperature dependence of the band-to-band transition within the context of an analytical model of photoluminescence and discuss the agreement between the modeling results and external device parameters such as the open circuit voltage of the solar cells over this broad temperature range.