Quantitative Extraction of the Self-Absorption Probability in Quantum Dot Color Conversion Films and Its Modulation...

Self-absorption limits efficiency and causes spectral redshift in quantum dot color conversion (QDCC) films, yet it is usually inferred indirectly rather than measured. In this study, we extract the self-absorption probability quantitatively from film photoluminescence (PL) spectra using the correction method of Ahn et al. The films span a wide thickness range at two quantum dot (QD) concentrations, with and without TiO₂. The converted emission peak wavelength scales linearly with the extracted self-absorption probability. For a given TiO₂ condition, this relation is independent of QD concentration. The self-absorption probability increases with both film thickness and QD concentration, reflecting longer optical path lengths and more reabsorption events. The intrinsic quantum yield from the same analysis is thickness-independent within each condition, supporting the extracted values. The addition of TiO₂ increases blue light absorption and lowers the extracted self-absorption probability of the converted emission, consistent with enhanced light scattering. With TiO₂, the remaining self-absorption is concentrated toward shorter wavelengths, producing a larger peak shift at comparable self-absorption probability. The external quantum efficiency increases with thickness at the lower concentration but not at the higher one, reflecting the competition between blue absorption and self-absorption.