Photoinduced Triplet Depletion Allowing Higher-Resolution Afterglow

Afterglow emission allows for imaging that is independent of autofluorescence under ambient conditions. Although higher-resolution afterglow is required for increasing the quality of the autofluorescence-free emission imaging, increasing the excitation intensity to generate brighter afterglow emission decreases the resolution of afterglow images. Therefore, methods and materials that provide afterglow imaging with higher resolution remain to be developed. In this study, we performed photoinduced triplet depletion and demonstrated improved resolution of bright afterglow emission using the depletion. Triplet depletion is related to charge separation via photoionization from a triplet state caused by depletion and subsequent rapid singlet formation. Triplet excitons that accumulated in a solid material by excitation were depleted under irradiation using a depletion beam with a longer wavelength than the absorption wavelength of the material. A higher-resolution afterglow image with an improvement of 25% was obtained by simultaneously focusing a donut-shaped depletion beam and an excitation beam.