Anthracene single crystals are grown by the Bridgman method under various conditions, and the quality estimation of the crystals is made from their triplet lifetime. The growth conditions for crystals with least defect are experimentally investigated. The best class of crystal is obtaiued when C
eq, which is defined by three main parameters, namely, temperature difference between an upper furnace and a lower one, down velocity of the ampoule, and cross section of the ampoule, and cross section of the ampoule, has the value of 180. It is suggested that the temperature difference is a more appropriate factor for determining growth condition rather than the temperature gradient.
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