Circular economy of ITO thin films deposited on glass obtained from degraded OLED devices

Emerson Roberto Santos,Wang Shu Hui,Lucas Henrique Silva De Jesus,Elvo Calixto Burini Junior,Roberto Koji Onmori

doi:10.17563/rbav.v40i1.1209

Abstract

In this work, circular economy was investigated for commercial indium tin oxide (ITO) thin films deposited on glass substrates obtained from degraded organic light-emitting diodes (OLED). These devices were assembled and polarized at laboratory in a previous work. For each substrate, with geometry 2.5 × 2.5 cm, four OLEDs with active area of 3 × 3 mm were set up. These OLED devices were assembled with ITO as the electrode anode and successive depositions of other materials (layer-by-layer), to form the complete structure. To obtain the recovered ITO, all layers were removed from the samples containing the OLEDs previously mounted, remaining only the ITO thin films, that were cleaned with commercial product together with the received ITO/glass samples. Both samples were compared using some techniques, such as: colorimetry, electrical resistance, and Raman spectroscopy. A methodology with light-emitting diode (LED) device polarized emitting light crossing the ITO thin films was used, and the luminance with chromaticity coordinates was obtained, revealing the good transparency of the thin films. Electrical resistance of recovered ITO revealed five higher orders of magnitude in comparison to the one of received ITO. This fact can be tributed to a poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) layer, causing corrosion of the ITO thin films during the assembly of OLEDs or loss of the field lines created during the electrical measurements by probes of four-point probe. Raman spectroscopy did not show satisfactory results in the chemical composition analyses of the samples, but it indicated good cleaning process of the samples before the analyses.

Highlights

Organic light-emitting diodes (OLEDs) can be characterized as electroluminescent semiconductor devices that uses multilayer structures of organic materials[1,2]
OLEDs have allured the interest of some companies because they have been used as displays substituting the traditional liquid crystal displays (LCDs) with superior advantages, such as: highest brightness, wide view angle (~170o), color reproduction fidelity, high sharpness and low response time[8,9]
Both received and recovered indium tin oxide (ITO)/glass substrates were placed in front of the polarized LED at the same conditions using only the LED

Summary

Introduction

Organic light-emitting diodes (OLEDs) can be characterized as electroluminescent semiconductor devices that uses multilayer structures of organic materials[1,2]. OLED devices were presented in 1987 by two researchers of Eastman Kodak Company known as Ching Wang Tang and Steven Van Slyke[5]. They announced the creation of an OLED device involving organic materials with multilayer structure such as glass/indium tin oxide (ITO)/diamine/8-tris-hydroxyquinoline aluminum (Alq3)/magnesium (Mg): silver (Ag)[5]. The OLED application in displays with flexible substrates for consumer products has been released by some companies as: Samsung, LG, Motorola and Huawei[10,11,12]

Methods

Results

Conclusion