Direct observations of energy transfer and quenching dynamics between Alq3 and C545T in thin films with different doping concentrations

Abstract

In this paper, we conducted photoluminescence (PL) and time-resolved photoluminescence (TRPL) measurements for the organic films that was composed of tris(8-hydroxyquinoline) aluminum (Alq₃) as the host and 10-(2-benzothiazolyl)-1, 1, 7, 7-tetramethyl-2, 3, 6, 7-tetrahydro-1H, 5H, 11H, [l] benzo-pyrano [6,7,8-ij] quinolizin-11-one (C545T) as the green dopant with different concentration. Typical quench behavior was observed by typical PL measurements when doping concentration exceeds 2% and the carrier lifetime decreased monotonically with increasing doping concentration in TRPL measurements. Time constant for energy transfer from host to dopant decreased with increasing dopant concentration and saturated above 2% dopant concentration. An anomalous blue shift at the initial probe time-interval was observed when dopant concentration was over 4%. It indicated a fast event energy absorption and/or relaxation process which had a time constant less than two picosecond. Two physical mechanisms with different time constant was observed those accounted for the concentration quench behaviors in the Alq3/C545T system.