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DOE OSTI · 3017091

Upconversion on the Micrometer Scale: Impact of Local Heterogeneity

Sullivan, Colette M.·Chen, Jia-Shiang·Ma, Xuedan·Wieghold, Sarah·Nienhaus, Lea
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Abstract

The properties of perovskite/naphtho[2,3-a]pyrene (NaPy) upconversion devices are investigated by a combination of atomic force microscopy and photoluminescence mapping to understand the role of microscopic heterogeneity in the ensemble device properties. The results emphasize strong microscopic inhomogeneity across the perovskite/NaPy upconversion device due to local formation of NaPy microcrystals. NaPy shows emission from three distinct states in the solid state: S 1 ′ emission at 520 nm, excimer emission at 560 nm, and S 1 ″ emission at 620 nm. Clear spatial differences in the emission spectrum under 405 nm excitation are found, highlighting that there is a strong microcrystal-to-microcrystal variation in the optical properties─emphasizing a need for multimodal measurements. Furthermore, our results indicate that microcrystals with strong emission from the strongly coupled low-energy state S 1 ″ (J-dimer) show much higher upconversion intensity than those with dominant emission from the high-energy S 1 ′ state (I-aggregate). Hence, our results suggest that microcrystals with strong emission from the low-energy state S 1 ″ act as isolated hotspots for upconversion.

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Sullivan, Colette M., Chen, Jia-Shiang, Ma, Xuedan, Wieghold, Sarah, Nienhaus, Lea. 2024-11-20. Upconversion on the Micrometer Scale: Impact of Local Heterogeneity. https://doi.org/10.1021/acs.jpclett.4c03075

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