Gravure printed flexible small-molecule organic light emitting diodes

Small-molecule based flexible organic light-emitting diodes (SMOLEDs) were fabricated by gravure printing. In order to modify rheological properties of the functional ink, the green emitter was embedded into an ultrahigh molecular weight polystyrene (UHMW-PS) matrix. The viscosity of the ink was characterized as a function of the small molecule:UHMW-PS weight ratio and solvent type. The gravure printed SMOLEDs exhibited a maximum luminance of 850 cd m⁻², a maximum efficiency of up to 7.7 cd A⁻¹, and turn on voltage of ∼3.5 V. The gravure printed SM:UHMW-PS device exhibits ∼67% higher luminance efficiency comparing to the spin-coated pristine SM device.