Uniform and bright light emission from a 3D organic light-emitting device fabricated on a bi-convex lens by a vortex-flow-assisted solution-coating method

Abstract

We herein present the results of a study on the novel fabrication process of uniform and homogeneous semiconducting polymer layers, in this case hole-injecting and fluorescent light-emitting layers that were produced by a simple solution-coating process for 3D conformal organic light-emitting diodes (3D OLEDs) on curvilinear surfaces. The solution-coating process used was a newly developed method of vortex-flow-assisted solution-coating with the support of spinning of the coating solution. It is shown that the vortex-flow-assisted spin-coating process can produce high-quality thin films at nanoscale thicknesses by controlling the liquid surface of the coating solutions, which can easily be adjusted by changing the spinning speed, even on complex curvilinear surfaces, i.e., a quasi-omnidirectional coating. This excellent film-forming ability without any serious film defects is mainly due to the reduction of line tension among the solution, air, and the substrate at the contact line due to vortex flows of the coating solution on the substrate during the vortex-spin-coating process. As a proof of concept, we present vortex-spin-coated 3D OLEDs fabricated on bi-convex lens substrates which exhibit excellent device performance with high brightness and current efficiency levels comparable to those of a conventional spin-coated 2D planar OLED on a flat substrate. It is also shown that the EL emission from the 3D OLED on the bi-convex lens substrate exhibits a diffusive Lambertian radiation pattern. The results here demonstrate that the vortex-flow-assisted spin-coating process is a promising approach for producing efficient and reliable next-generation OLEDs for 3D conformal opto-electronics.

Semiconductor/dielectric interface in organic field-effect transistors: charge transport, interfacial effects, and perspectives with 2D molecular crystals

“…When the electric field applied from the gate electrode modulates the channel conductivity, the gate dielectric always has a decisive influence on the charge transport behaviours [17][18][19]. Therefore, understanding of the nature of charge carriers at the semiconductor/dielectric interface is of great importance for clarifying the structureproperty relationships and achieving high-performance OFET devices, which have been the cornerstones for the sustainable advancement in organic electronics [20][21][22][23]. For the characterizations of the interface, numerous optical and electrical technologies are introduced, such as synchrotron-based high-resolution ultraviolet photoelectron spectroscopy and scanning Kelvin probe microscope measurements [24][25][26].…”

Solution-processed OLEDs for printing displays

“…Secondly, when multilayer devices are prepared by the spin-coating method, the solution in the upper layer may dissolve the solution in the former layer, resulting in an uneven morphology of the overall film, inhibiting the effect of each functional layer, and thus resulting in low device efficiency. 199…”

“…Secondly, when multilayer devices are prepared by the spin-coating method, the solution in the upper layer may dissolve the solution in the former layer, resulting in an uneven morphology of the overall film, inhibiting the effect of each functional layer, and thus resulting in low device efficiency. 199 Researchers have also put forward many measures to improve the above problems. In 2015, Cho et al reported a method to change the molecular solubility and luminescence color by introducing F as electron withdrawing.…”

Plasma-enhanced atomic layer deposition of nickel and nickel oxide on silicon for photoelectrochemical applications

“…Pulsed laser deposition, spin coating, sputtering and atomic layer deposition (ALD) are common methods of NiO film preparation previously reported in the literature, with spin coating being the more common approach due to its comparative simplicity and equipment requirements [19][20][21][22]. However, spin coating falls short in offering a high level of controllability of film thickness as well as poor surface coverage and wettability, particularly when the base substrate is especially rough, resulting in the introduction of interfacial defects [16,23].…”