Vg. Kozlov et al., Optical properties of molecular organic semiconductor thin films under intense electrical excitation, APPL PHYS L, 74(8), 1999, pp. 1057-1059
Using electro-optical pump and probe measurements, we studied optical prope
rties of a thin film of tris-(8-hydroxyquinoline) aluminum (Alq(3)) doped w
ith DCM2 laser dye under pulsed injection currents as high as 300 A/cm(2).
Pump-induced transparency and absorption were observed in the spectral rang
es of 570-610 nm and 620-705 nm, respectively. We attribute these optical e
ffects to molecular polarons formed under electrical excitation. Polaron ab
sorption dominates the optical properties of electrically pumped Alq(3):DCM
2 films in the spectral range where optical gain is anticipated (i.e., from
630 to 700 nm). Polaronic effects may present a significant obstacle for r
ealization of organic diode lasers based on this material system. (C) 1999
American Institute of Physics. [S0003-6951(99)00108-4].