Overcoming the Limitations of MXene Electrodes for Solution-Processed Optoelectronic Devices

Abstract

MXenes constitute a rapidly growing family of 2D materials that are promising for optoelectronic applications because of numerous attractive properties, including high electrical conductivity. However, the most widely used titanium carbide (Ti3C2Tx) MXene transparent conductive electrode exhibits insufficient environmental stability and work function (WF), which impede practical applications Ti3C2Tx electrodes in solution-processed optoelectronics. Herein, Ti3C2Tx MXene film with a compact structure and a perfluorosulfonic acid (PFSA) barrier layer is presented as a promising electrode for organic light-emitting diodes (OLEDs). The electrode shows excellent environmental stability, high WF of 5.84 eV, and low sheet resistance R-S of 97.4 omega sq(-1). The compact Ti3C2Tx structure after thermal annealing resists intercalation of moisture and environmental contaminants. In addition, the PFSA surface modification passivates interflake defects and modulates the WF. Thus, changes in the WF and R-S are negligible even after 22 days of exposure to ambient air. The Ti3C2Tx MXene is applied for large-area, 10 x 10 passive matrix flexible OLEDs on substrates measuring 6 x 6 cm. This work provides a simple but efficient strategy to overcome both the limited environmental stability and low WF of MXene electrodes for solution-processable optoelectronics.