Characteristics of electron injection at the oxide electrode/polyethylenimine ethoxylated/Alq₃ interface

Abstract

Inverted organic light-emitting diodes (inverted OLEDs) require electron injection to an organic semiconductor from a transparent oxide electrode. Polyethylenimine ethoxylated (PEIE) has attracted considerable attention as an electron injection material. An injection mechanism has been suggested; however, the barrier height of electron injection has not been determined. In this paper, we present the experimental values for the electron injection barrier height at the transparent oxide electrode/PEIE/organic semiconductor interface. Electron-only devices, consisting of indium-tin-oxide (ITO)/PEIE/tris(8hydroxyquinolinato) aluminum (Alq3)/Al, are fabricated. The temperature dependence of the current-voltage curves is measured corresponding to the electron injection of the ITO/PEIE/Alq3 interface. The current-voltage curves are found to be independent of the measurement temperature, which is explained by the tunneling model. The tunneling injection barriers height are calculated, and the experimental injection barrier height will be important for the development of inverted OLED devices.

Perovskite Photo-Sensors with Solution-Processed TiO2 under Low Temperature Process and Ultra-Thin Polyethylenimine Ethoxylated as Electron Injection Layer

“…Figure 2 shows the FE-SEM observation on the TiO 2 layer fabricated by the CBD method [33]. The surface morphology was comparatively flat and grain size was observed between 0.1 and 1 µm.…”

“…During this time, we studied the PePS with a solution-processed TiO 2 at a low temperature of 70 • C by the chemical bath deposition (CBD) method [29]. For improving device performance, an ultra-thin polyethylenimine ethoxylated (PEIE) [30][31][32][33] as an electron injection layer is fabricated and device characteristics are evaluated. One of the preliminary experimental results is presented at the international conference on the 26th and 27th International Workshop on Active-Matrix Flatpanel Displays and Devices [34,35].…”

Hole Injection Characteristics and Annealing Temperature Dependence for Organic Light‐Emitting Diodes Using Spontaneous Polarization

“…Among these, carrier injection enhancement by permanent electric dipoles formed at the electrode/ organic semiconductor interface has been reported in many cases, and OLED and organic solar cell devices using cationic polymers, such as polyethyleneimine (PEI) and polyethyleneimine ethoxylated (PEIE), have been reported as electron injection materials. [21][22][23] The thickness of OLEDs with these polymer layers does not increase, because these polymer layers are ultrathinned by treatment.…”