Abstract
Inkjet printing technique allows manufacturing low cost organic light emitting diodes (OLEDs) in ambient conditions. The above approach enables upscaling of the OLEDs fabrication process which, as a result, would become faster than conventionally used vacuum based processing techniques. In this work, we use the inkjet printing technique to investigate the formation of thin active layers of well-known light emitting polymer material: Super Yellow (poly(para-phenylene vinylene) copolymer). We develop the formulation of Super Yellow ink, containing non-chlorinated solvents and allowing stable jetting. Optimization of ink composition and printing resolution were performed, until good quality films suitable for OLEDs were obtained. Fabricated OLEDs have shown a remarkable characteristics of performance, similar to the OLEDs fabricated by means of spin coating technique. We checked that, the values of mobility of the charge carriers in the printed films, measured by transient electroluminescence, are similar to the values of mobility measured in spin coated films. Our contribution provides a complete framework for inkjet printing of high quality Super Yellow films for OLEDs. The description of this method can be used to obtain efficient printed OLEDs both in academic and in industrial settings.
Highlights
Www.nature.com/scientificreports optimize the ink and the printing parameters to avoid such undesirable effects
We discovered that the inks with concentration of Super Yellow exceeding 0.5 mg/mL are non-jettable
We demonstrated that the inkjet printing technique can be successfully adopted for fabrication of light emitting layers based on the well-known light emitting polymer- Super Yellow
Summary
Influence of solvent and polymer concentration on inkjet printing. Toluene is the most common solvent used for preparation of Super Yellow solutions[19,20,22]. The emission spectra of both spin coated and printed films are similar to each other, and the emission band in the solid state is red shifted in comparison to the solution (see Supplementary Fig. 6Sb) This is likely caused by aggregation[32]. The effective Poole-Frenkel coefficient in spin coated and inkjet printed film is −5.4 × 10−4 (cmV−1)1/2 and −5.7 × 10−4 (cmV−1)1/2 respectively, see Supplementary Table S6
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