Study of variation in thickness of poly(n-vinylcarbazole) [PVK] thin films in different solvents for static dispense spin coating method

We report the effect of evaporation rate of solvents (chloroform and chlorobenzene) over the thickness of spin coated PVK thin films and turn-on voltage of fabricated organic light emitting devices(OLEDs). In our work, experiments are performed for static dispense spin coating procedure in which the dispensed drops of PVK solution are made to wait for a finite time before spinning. It is found that the high evaporation rate solvent has higher sensitivity to wait-time-to-spin as opposed to low evaporation rate solvent. The increased turn-on voltage for devices with high evaporation rate solvent proved that the thickness of PVK thin film increases with wait time for chloroform. We observed relatively lesser change in turn-on voltages for chlorobenzene based OLEDs possibly because of low evaporation rate resulting in smaller changes in thickness of PVK layer.