Recycling indium tin oxide (ITO) anodes for use in organic light-emitting diodes (OLEDs)

Abstract

Electrodes in many thin-film optoelectronic devices are made of layers of indium tin oxide (ITO), which are suitably conductive, can be deposited by established methods, and are nearly transparent and colorless. Regrettably, indium is an uncommon element, its price continues to rise steeply, and producing ITO electrodes consumes a large fraction of the total energy needed to make thin-layer devices. Nevertheless, ITO electrodes are widely used in devices, both in research and industrial production. The growing commercial importance of these devices creates an urgent need for ways to ensure sustainability, such as by recovering ITO from devices no longer needed or even by recycling intact ITO electrodes. Recent work has shown that patterned ITO electrodes can be recovered from organic thin-film photovoltaic devices (OPVs) after simple exposure to water or dilute aqueous base, and then reused in new devices with essentially no decrease in performance. We now report that similar approaches can be used to recover and reuse ITO electrodes in organic light-emitting diodes (OLEDs), which are currently manufactured in much greater numbers than OPVs. Use of atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) to study the surfaces of ITO electrodes recovered from OLEDs revealed minor changes in morphology, but the performance of the recycled electrodes in new OLEDs proved to be virtually unchanged, even after multiple cycles of recovery and reuse.