Transient absorption microscopic study of triplet excitons in organic crystals

We have constructed a transient absorption microscope to study triplet excitons in organic crystals. Using the microscope, transient absorption of small crystals can be measured and the spatial distribution of triplet excitons can be obtained. Additionally, it was found that the contrast of the image becomes much better than that of a conventional bright-field microscope. These characteristic features of the transient absorption microscope will be discussed. We also report on the absorption spectra in benzophenone, anthracene and α- and β-perylene crystals. Absorption spectra due to triplet excitons in the crystals were similar to the corresponding solution spectra, although there were some minor differences.