2018-742 A GENERAL SOLUTION-PROCESSABLE APPROACH TO HIGH-QUALITY TWO-DIMENSIONAL INK MATERIALS FOR PRINTABLE HIGH-PERFORMANCE LARGE-AREA AND LOW-COST ELECTRONICS/OPTOELECTRONICS/THERMOELECTRICS

A General Solution-Processable Approach To High-Quality Two-Dimensional Ink Materials For Printable High-Performance Large-Area And Low-Cost Electronics/Optoelectronics/Thermoelectrics

SUMMARY

UCLA researchers in the Departments of Chemistry & Biochemistry and Materials Science & Engineering have developed a general and cost-effective solution-phase approach to create large-area and high-performance thin films or devices.

BACKGROUND

2D layered materials beyond graphene are a unique research area with important electronic, optical, and catalytic properties. For example, molybdenum disulfide (MoS₂) is widely studied because it is abundant and has suitable performance properties for electronic devices. However, current synthetic methods for preparing 2D materials, such as chemical vapor deposition or mechanical exfoliation, are expensive and time-consuming. Development of solution-processable methods would enable scalable syntheses of these materials, however current solution-processable materials exhibit lower electrical mobility (0.4 cm²V^-1s²) in thin film transistors than those with materials made by conventional means (30 cm²V^-1s²). An approach that enables scalable preparation of high-quality 2D materials is essential in order to further develop the applications of these materials.

INNOVATION

Professors Duan and Huang have developed a novel method of producing high-quality MoS₂ semiconducting nanosheets using solution processing. In this approach, 2D MoS₂ crystals are electrochemically intercalated with various large organic ammonium salts to form nanosheets, which can be subsequently formulated into an ink solution with concentrations up to 20 mg/mL. The materials can be further processed into thin films, enabling production of large-area thin film transistors with electron mobilities of 10 cm²V^-1s² and on/off ratio >10⁶. Nanosheet ink solutions can additionally be deposited onto plastic substrates, enabling development of flexible/wearable devices.

APPLICATIONS

• Electronics
• Printable electronics
• Flexible/wearable devices
• Optoelectronics
• Superconductors
• Thin film transistors
• Thermal managing
• Catalysis

ADVANTAGES

• General method can be applied to a variety of 2D layered materials, including MX (M=Ge, Sn; X=S, Se, Te, As), MX₂ (M=Mo, W, Sn, V, Nb, Ta, Pt; X=S, Se, Te), M₂X₃ (M= Bi, Sb, Ga, In; X=Se, Te)
• Identity of organic ammonium salts can be structurally varied
• Low-cost and scalable method
• Improved field-effect mobility (10 cm²V^-1s²) compared to previous state-of-the-art (<0.4 cm²V^-1s²)
• Improved on/off ratio (>10⁶) compared to previous state-of-the-art (10²)

STATE OF DEVELOPMENT

Method has been demonstrated and used to prepare large-scale thin film transistors.