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 RS of 97.4 Ω 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 RS are negligible even after 22 days of exposure to ambient air. The Ti3C2Tx MXene is applied for large‐area, 10 × 10 passive matrix flexible OLEDs on substrates measuring 6 × 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.

Graphene Oxide‐Assisted Multiple Cross‐Linking of MXene for Large‐Area, High‐Strength, Oxidation‐Resistant, and Multifunctional Films

“…[2c,4] Compared with stainless steel or solid copper with SSE values of ≈30 dB cm 2 g −1 , [5] MXenes demonstrate significant potential for lightweight, flexible, highperformance EMI shields. MXene-based flexible piezoresistive sensors, [6] supercapacitors, [7] and electrodes [8] have also been developed with huge application potentials. Despite the impressive progress of MXene-based functional macrostructures, the unsatisfactory mechanical strength derived from the poor interfacial interactions between MXene flakes, inferior oxidation stability of MXenes in H 2 O/O 2 conditions, and limited scalable manufacturing, block their applications.…”

Recent progress in energy, environment, and electronic applications of MXene nanomaterials

“…This leads to oxidation, resulting in a reduced work function. 91 To overcome this drawback and to maintain the transparency of films, Zhou et al introduced a perfluorosulfonic acid barrier layer. After the surface treatment with perfluorosulfonic acid, Ti 3 C 2 T x MXene shows a 5.84 eV work function which initially was 4.89 eV.…”

“…After the surface treatment with perfluorosulfonic acid, Ti 3 C 2 T x MXene shows a 5.84 eV work function which initially was 4.89 eV. 91 To study the optoelectronic properties, Hantanasirisakul et al prepared Ti 3 C 2 T x and used a different etchant, Ti 3 CNT x , and compared their light-absorbing abilities. 92 They used HF + TMAOH and LiF + HCl etchants to prepare Ti 3 CNT x and LiF + HCl to prepare Ti 3 C 2 T x .…”

Ti3C2Tx MXene: A New Promising 2D Material for Optoelectronics

“…MXene thin films by various chemical treatments 98,99 is reported to improve the environmental stability in optoelectronic devices. Thus, enhancing the oxidation stability of MXene is identified as crucial for maintaining its unique optical as well as electronic properties, enabling its practical use in optoelectronics.…”