The effect of low temperature thermal annealing on the properties of organic light‐emitting device

Abstract

PurposeThe purpose of this paper is to study the effect of on device performance by selectively annealing ITO substrates and TPD:PVK layers of the OLED at different temperatures with a certain annealing time.Design/methodology/approachThermal annealing was carried out on the ITO anode at different temperatures (150, 350, 500°C) with a constant time (100 min); but also before the deposition of the tris(8‐hydroxyquinolato) aluminum (Alq3) layer, at the same time, thermal treatment was carried out on the hole transporting layers (TPD:PVK layers) at different temperatures (70, 90, 110°C), and the annealing time was 30 min. We fabricated a novel device with the structure of Al/LiF/Alq3/TPD:PVK/NiO/ITO/Glass, and tested the sheet resistance, SEM and XRD of ITO anode after annealing, at the same we also tested the I‐V, L‐V and current efficiency characteristics of OLED.FindingsWhen the TPD:PVK layers were annealed at 90°C with 30 min annealing time and ITO substrates were annealed at 350°C with a constant annealing time (100 min), we find that the OLED shows obvious performance improvement, which is attributable to the fact that annealing reduces defects and improves the interface structures of organics and organic/ITO interface. On the other hand, an annealing TPD:PVK layers would slow and even impede the transport of holes, and finally leads to more balanced electron and hole injection processes.Originality/valueThe paper shows that the annealing method can be used to prepare high‐performance organic light‐emitting device.