Research Fields

Perovskite and Metal Halide Semiconductors for High Performance Thin-Film Transistors

The past two decades have witnessed the enormous success of metal halide perovskite semiconductors in various optoelectronic devices, like solar cells, LEDs, and most recently transistors, due to an ideal set of optoelectronic properties and processing capability. In particular, considering the urgent demand for high-mobility p-type semiconductors, metal halide perovskite provides a new opportunity to create CMOS circuits in a low-temperature and cost-effective way. Despite certain performance improvements that have been achieved through material design, film processing, and device engineering, a critical understanding of the key properties and potential of these emerging materials for transistor application remains lacking. Therefore, we intend to develop halide perovskite semiconductors for high performance p-type thin-film transistors for commercialization. This project mainly studies the topics below but not limited to this.

• Development of new lead-free halide perovskite materials for semiconducting layer in TFTs for application of flat panel display and CMOS circuits.

• Understanding structure-properties relationship and charge transport physics in halide perovskite film.   

• Development of perovskite thin film deposition (printing and high vacuum-based), patterning, and etching process and optimization of fabrication processes.

• Demonstration of large-area TFT array and CMOS integrated circuits and M3D devices on the conventional and unconventional substrate.  

2D Layered Semiconductors for High-Performance Thin-Film Transistors

The 2D materials family has been ever-growing to thousands of members with different electronic properties, from metals, semiconductors, insulators to superconductors. Solution-processable two-dimensional (2D) van der Waals thin films have drawn extensive attention for next-generation printable and flexible electronics due to their superior charge transport properties and cost-effective facile processes. However, the characteristics of solution-processed CMOS circuits and other electronic devices composed of n-type and p-type TFTs with van der Waals films are still in their preliminary stage compared to the great expectations. A better understanding of the transport properties in the intra-flake and inter-flake, and the interface properties between different functional 2D materials in thin films, could offer rational design strategies to realize high-performance devices, and hence for van der Waals integration. Below are a few examples of the current and future research interests of our group:

• Development of solution processing of 2D materials, including metal, semimetal, semiconductor, and insulator materials.

• Understanding the charge transport properties and interface properties of solution-processed 2D thin films.

• Development of high-performance field-effect transistors by doping, defect and interface engineering, and contact engineering.

• Development thin film deposition, patterning, and etching process for fabrication of 2D electric devices.

• Van der Waals integration for electronics and optoelectronics devices, such as CMOS, logic circuits, sensors, imaging, and 3D electronics.

Synthesis of Perovskite Nanocrystal for High-Performance Light-Emitting Devices 

The halide perovskite have excellent optoelectronic properties, such as high luminous efficiency and color purity, and wide color gamut. In particular, low-dimensional perovskite nanocrystals with high exciton binding energy have the potential for high-performance light-emitting devices. However, understanding the key properties of perovskite nanocrystal synthesis, ligand engineering and charge transport layer is not fully explored. Therefore, the focus of our research is on the following topics.

• Development of new synthesis methods of halide perovskite (lead and lead-free) nanocrystals for high performance and stability light-emitting devices.

• Understanding of the charge transport properties and defect with surface ligand of perovskite nanocrystals.

• Development of new charge transport layer with high mobility, vertical film deposition (printing and evaporation), and ligand engineering (facile charge transport, defect passivation, core-shell, and cross-linking) for fabrication of perovskite-based light-emitting devices.

• Demonstration of patterned R, G, B emitting perovskite-based devices (diodes and transistors) for display and laser.