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Imaging local luminescence variations in CdSe0.1Te0.9 thin films grown by the colossal grain growth process.



Ganga Neupane, Andrew Winchester, Nicolas Marquez Peraca, David Albin, Joel Duenow, Matthew Reese, Sujitra Pookpanratana, Susanna Thon, Behrang Hamadani


Clear visualization and understanding of luminescence properties of grain interiors and grain boundaries in polycrystalline thin-film photovoltaic materials are crucial to achieving high-performance solar cells. Luminescence-based measurements, for example, reveal sub-bandgap energetic disorder or impurity-related radiative transitions in these materials, and when performed in the absolute scale, they can show the extent of voltage-limiting non-radiative recombination. Here we use a hyperspectral imaging technique to investigate inter- and intra-grain photoluminescence variations in polycrystalline CdSe0.1Te0.9 films made by the colossal grain growth process. We observe that grain boundaries show higher luminescence than grain interiors for all energies below the bandgap energy. Multiple distinct sub-bandgap defect transitions are detected and determined to be related to donor-acceptor pair impurities. A comparison of the excitation-intensity-dependent photoluminescence at the grain boundaries with grain interiors suggests that carrier concentration is higher at grain boundaries. This finding is supported by photoemission electron microscopy imaging of the films, showing 70 meV upward energy shift in the band structure at the grain boundaries. Finally, we investigate a dramatic thermal quenching behavior related to the donor-acceptor pairs luminescence over a temperature range and use a rate-equation model to attribute it to the sudden redirection of the radiative recombination channels to non-radiative channels with increasing temperature.
Cell Reports Physical Science


CdSeTe, hyperspectral imaging, thin films, grain interior, grain boundary, PL quenching, donor-acceptor pair recombination, photoelectron emission microscopy, rate-equation model, external radiative efficiency


Neupane, G. , Winchester, A. , Marquez Peraca, N. , Albin, D. , Duenow, J. , Reese, M. , Pookpanratana, S. , Thon, S. and Hamadani, B. (2023), Imaging local luminescence variations in CdSe0.1Te0.9 thin films grown by the colossal grain growth process., Cell Reports Physical Science, [online],, (Accessed July 15, 2024)


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Created August 4, 2023, Updated September 19, 2023