Université Grenoble-Alpes, CEA, Leti, MINATEC Campus, 17 rue des Martyrs, Grenoble, France, CEISAM - CNRS UMR 6230, Université de Nantes, 2 rue de la Houssinière, Nantes, France

The QUPD molecule has been deposited by inkjet printing as a hole-transport layer in top-emitting green OLEDs. A systematic study of the QUPD-based ink formulation has been done and different solvent mixtures have been investigated, in order to find the best composition (QUPD in toluene/IPA/anisole, 8/1/1 v/v/v) leading to the best film forming properties. Spin-coated PEDOT-PSS has been used as hole injecting layer. Subsequent layers have been deposited by vacuum sublimation. The resulting hybrid, solution-sublimation, OLEDs have been encapsulated by atomic layer deposition using Al2O3 material. In order to overcome the issue related to the thickness control of the organic layers deposited from solution, second order cavity length OLEDs have been fabricated by modifying the n-doped electron transport layer thickness. In that case, the relative OLED efficiency variation (10.5%) due to the thickness variation is far less compared to first order cavity length (34%) allowing a better reproducibility of the OLED fabrication. In the end, high efficiency (18 lm/W) green OLEDs of two different sizes, 0.44 cm2 and 4 cm2, have been fabricated, using an inkjet printed QUPD layer as hole transporting layer. © 2017 Elsevier B.V.

Inkjet printing thin-film encapsulation, OLED, Solution-deposition technique

Atomic layer deposition, Efficiency, Fabrication, Ink jet printing, Molecules, Printing, Sublimation, Electron transport layers, Film-forming properties, Hole transport layers, Hole transporting layers, OLED, Solution deposition techniques, Thickness variation, Thin film encapsulation, Deposition