My research focuses on the realization of next-generation electronics with flexibility/stretchability by utilizing organic, inorganic, and hybrid materials. I not only work on basic thin-film transistors but also other electronic devices including solar cells, light-emitting diodes, batteries, and relevant integrated circuits. The potential applications of these electronic devices include but are not limited to displays, energy storage&generation, e-textiles, human interactivity, healthcare.
Here are some representative works:
Metal Oxide with polymer incorporation
Metal oxide (MO) (semi)conductors have attracted great attention for next-generation electronics because of their high carrier mobilities, optical transparency, and air stability. Nowadays, commercialized metal oxide (semi)conductors are fabricated by physical vapor deposition techniques, which are expensive and require photolithographic patterning, thus limiting roll-to-roll fabrication. In recent years, solution processing has emerged as an alternative way to deposit/pattern metal oxide (semi)conductors, but transistor performance is below that of physical deposited MOs. Polymer incorporation in metal oxide matrices holds the potential to yield enhanced performance on solution-processed metal oxide. Incorporating the functionalities of polymers into MO semiconductors can be achieved, leading to metal oxide transistors with mechanical flexibility, transparency, and high mobility. Moreover, polymer incorporation is an effective way to manipulate the solution rheological properties, making the precursors compatible with various printing techniques, including blade-coating, aerosol jet printing, and brush printing.
Figure. SEM images of metal oxide films with different polymer loading.
Figure. Mobility of different neat semiconducting oxides, and optimal oxides-polymer blends.
Organic Transistors for High‐Sensitivity NO2 Detection
A new type of nitrogen dioxide (NO2) gas sensor based on copper phthalocyanine (CuPc) thin film transistors (TFTs) with a simple, low‐cost UV–ozone (UVO)‐treated polymeric gate dielectric is reported here. The NO2 sensitivity of these TFTs with the dielectric surface UVO treatment is ≈400× greater for [NO2] = 30 ppm than for those without UVO treatment. Importantly, the sensitivity is ≈50× greater for [NO2] = 1 ppm with the UVO‐treated TFTs, and a limit of detection of ≈400 ppb is achieved with this sensing platform. The morphology, microstructure, and chemical composition of the gate dielectric and CuPc films are analyzed by atomic force microscopy, grazing incident X‐ray diffraction, X‐ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy, revealing that the enhanced sensing performance originates from UVO‐derived hydroxylated species on the dielectric surface and not from chemical reactions between NO2 and the dielectric/semiconductor components. This work demonstrates that dielectric/semiconductor interface engineering is essential for readily manufacturable high‐performance TFT‐based gas sensors.
Cofuel Assisted Combustion of LiMn2O4 for Li-ion Batteries
LiMn2O4 (LMO) spinels with diverse achievable morphologies are realized using solution processing techniques including sol-gel and cofuel-assisted combustion synthesis (CS). These LMOs are utilized as cathode materials in lithium-ion batteries (LiBs), with LMO produced here by low-temperature, sorbitol-assisted combustion synthesis (SA-CS) yielding superior performance metrics. Morphological analysis by combined X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy demonstrates that these SA-CS LMO powders have optimum LiB grain (<500 nm) and crystallite (~30 nm) dimensions as well as spinel phase purity. Cathode mixtures having micron-scale, uniformly distributed LMO, conductive carbon, and a polymer binder provide effective electron and Li transport as assessed by electrochemical impedance spectroscopy and fabricated battery performance, showing high capacity (~120 mA h/g), good cycling stability (~95% capacity retention after 100 charge/discharge cycles), and high charge/discharge rates (up to 86 mA h/g at 10 C). SA-CS provides a simple, efficient, lower temperature, and scalable process for producing morphology-controlled high-performance LiB cathode oxides.