Novel Surface Modification of Indium-Tin-Oxide Films Using Ion Implantation for Organic Light-Emitting Diodes

Abstract

Indium–tin–oxide (ITO) films doped using an ion implantation system were used as the anode electrode of organic light-emitting diodes (OLEDs). Changes in the characteristics of the doped ITO films were observed and measured in terms of sheet resistance, Hall mobility, contact angle, roughness, transmittance and work function. Boron dopant was used as an impurity to modify the surface of the ITO films. The depth profile of boron concentration was monitored by secondary ion mass spectrometry (SIMS) as a function of dose. Optimum dose was 5×1014 atoms/cm3 at which resistance was lowest. The resistance variation from 16 Ω/sq. of the conventional ITO to 11 Ω/sq. of doped ITO shows that the doped ITO films become more conductive after doping and thermal annealing. The Hall mobility and carrier concentration of boron-doped ITO was 40.4 cm2/Vs and -9.32×1020/cm3 respectively. Contact angle and roughness were investigated by the sessile drop technique and atomic force microscopy (AFM). After doping, the water contact angle of the film surface was changed from 55° to 38° and the root-mean-square roughness of the films was similar to that of conventional ITO. Transmittance in the visible spectrum range was increased from 91% to 96%. Work function was improved from 4.66 eV to 4.86 eV. An OLED device fabricated with a multilayer, boron-doped-ITO/CuPc/NPD/Alq3:C545T/Alq3/LiF/Al, was tested. The device had a luminance of 780 cd/m2 and the lifetime was also increased by approximately 25% compared with those of ITO devices produced under the same conditions.

Enhanced photovoltaic device performance upon modification of indium tin oxide coated glass by liquid nitrogen treatment

“…Moreover, this increase in transmittance is due to the incorporation or adsorption of N 2 into the ITO film that increases the film diffuse transmittance or due to the cooling effect. Choi et al [12] have observed the same trend after B-doping in the ITO film. However, an optical transmittance is closely related to oxygen vacancies, which are associated with free electrons in the ITO films as mentioned earlier.…”

Chemical properties of electrosprayed antimony tin oxide thin film/Ag nanowire multilayer for transparent conductive electrodes

“…T ransparent conductive electrodes (TCEs) that simultaneously provide low resistivity (<10 ¹3 ³0cm) and high transmittance (>80%) in the visible region are important components for optoelectronic applications such as solar cells, organic light-emitting diodes, and touch screens. [1][2][3] Until now, various TCE materials such as oxide-based materials [e.g., In 2 O 3 :Sn (ITO), SnO 2 :F (FTO), ZnO:Al (AZO), and SnO 2 :Sb (ATO)], carbon-based materials (e.g., graphene and carbon nanotubes), and metal-based nanowires (NWs) (e.g., Ag NWs and Cu NWs) have been extensively developed. [4][5][6] Among the above-mentioned materials, Ag NWs have recently been proposed as a promising candidate for TCEs because of their low sheet resistance and low extinction coefficient in the visible range.…”

Approaches for Long Lifetime Organic Light Emitting Diodes

“…[209,210] Choi et al reported boron doping affects the surface properties of ITO but increases the OLED performance because it influences surface energy, transmittance, sheet resistance, work function and mobility. [211] Zhou et al examined the sand blasting technique for creating surface roughness on OLED substrate, in order to reduce the wave nature of internally generated photons, which could increase the external quantum efficiency from 9% to 11.6%. [212] Hatton et al reported that Silane modified ITO shows better power efficiency as compared to normal ITO surface due to tune the anode work function to the HOMO of HTL.…”