Konzentrations-und Temperaturabhängigkeit der Sensibilisierten Verzögerten Fluoreszenz in Naphthalin/Anthracen-Mischkristallen / Sensitized Delayed Fluorescence in Naphthalene/Anthracene Mixed Crystals: Concentration and Temperature Dependence

Abstract

The delayed fluorescence of naphthalene crystals doped with anthracene has been investigated for concentrations between 7 × 10-9 and 10-5mol/mol in the temperature range 4.2 -300 °K. The concentration dependence of both the quantum ratio of host and guest emission and of the lifetime shows the effectivity of energy transfer by triplet excitons. It can be described quantitatively within the statistical hopping model, which includes the probability for an exciton to visit the same host molecules repetitively before becoming trapped. This incoherent energy transport becomes faster as the temperature is lowered. The exciton hopping time decreases monotonically from tʜ = 2 × 10-10 sec at 300 °K to tʜ = 8 × 10-11 sec at 130 °K. Below 100 °K the delayed fluorescence is governed by competing trapping effects.