Visualizing localized, radiative defects in GaAs solar cells

Behrang H Hamadani; Margaret A Stevens; Brianna Conrad; Matthew P Lumb; Kenneth J Schmieder

doi:10.1038/s41598-022-19187-4

Visualizing localized, radiative defects in GaAs solar cells

Sci Rep. 2022 Sep 1;12(1):14838. doi: 10.1038/s41598-022-19187-4.

Authors

Behrang H Hamadani¹, Margaret A Stevens², Brianna Conrad³, Matthew P Lumb⁴, Kenneth J Schmieder⁵

Affiliations

¹ National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA. behrang.hamadani@nist.gov.
² NRC Postdoc Residing at NRL, Washington, DC, 20375, USA.
³ National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA.
⁴ Formerly With George Washington University, Washington, DC, 20052, USA.
⁵ U.S. Naval Research Laboratory, Washington, DC, 20375, USA.

Abstract

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.