The Relation between the Electrical, Chemical, and Morphological Properties of Indium−Tin Oxide Layers and Double-Layer Light-Emitting Diode Performance

Abstract

The relation between the electrical, chemical, and morphological properties of indium-tin oxide (ITO) thin films and organic light-emitting diode (OLED) performance is studied. We report on chemical (HCl, piranha solutions), thermal (vacuum annealing), physical (oxygen plasma, UV ozone), and combined treatments on ITO layers. The effects of these different treatments have been studied using the four-point probe resistivity measurement method, contact angle measurement, X-ray diffraction, surface profilometry, and UV-vis-IR transmittance. Double-layer OLEDs with treated ITO as the anode and poly(9,9-dihexyl-9H-fluorene-2,7diyl) and 8-hydroxyquinoline aluminum salt as the hole transporter and emitting material, respectively, have been realized. The electrical and optical properties of OLEDs have been extensively investigated, and it is shown that UV ozone-HCl combined treatment yields the highest hole injection efficiency and luminance and the lowest drive voltage. For each OLED with treated ITO, the anode potential barrier height decrease is estimated using Fowler-Nordheim and Schottky-Richardson modeling of the electrical conduction.

The effect of ITO surface energy on OLED electrical properties

“…2-4 the OLED energy diagram, the current-voltage and the conductance vs. the sqrt of voltage are shown respectively. As reported in literature [7,8], at high voltages the HCl-UV treatment shows the best improvement in conductance increasing the current of over 400 times. In this first analysis the d-sample (Oxygen plasma treatment) is not considered because it shows strange electrical behaviour.…”

“…In fact ITO is used as anode due to its transparency in the visible range and good electrical conductivity. Many chemical-physical ITO surface treatments [1][2][3][4][5][6][7][8] have been optimized in order to reduce surface roughness, spikes and carbon impurities. These treatments control the surface constituent ratio, the surface energy and the polarity too.…”

One‐Step Fabrication of Bio‐Compatible Coordination Complex Film on Diverse Substrates for Ternary Flexible Memory

“…The TA‐Fe III film was grown on indium tin oxide (ITO) glass in a one‐step reaction as shown in Figure a following Caruso's paper . The ITO glasses were first treated with a piranha solution to enrich hydroxyl groups as indicated by the contact angle increase from 65.5 to 75.7° (see Figure S1) . TA has five branches of polyphenol groups and reacts with Fe 3+ [Figure a, (iii)] to slowly form a tri‐coordination complex when the solution is weakly basic (pH 8.0).…”

Enhanced performance of organic light-emitting diodes (OLEDs) and OLED-based photoluminescent sensing platforms by novel microstructures and device architectures

“…Such an injection current can be written as [47,48] OLED [49]. They compared the fit of the I-V characteristic with models based on thermionic emission and FN tunneling, as shown in Fig.1-4.…”