Optoelectronic Materials and Sensor Devices

Overview

These days, sensor devices have wide applications according to the rapid developments of technology. Our group developed a variety of materials such as TeO2 microwires, ZnO Nanoparticles/Nanowires, and ZnSnO3 Nanowires/Microwires for sensor applications in detecting physical motions, such as a pulse-driven sensor, air pressure, and touchless control of smart devices.

Our strategies:
Smart Sensor Devices

We successfully demonstrated an ultrasensitive wrist-wear pulse active sensor that was first made using tellurium dioxide (TeO2) triangular microwires. Thanks to the gravitational force effect, α-TeO2 microwires were encapsulated by polydimethylsiloxane (PDMS). The triangular TeO2 microwires have created an obviously piezoelectric potential (piezopotential) ~3.2 V that was perpendicularly established along with the poling axis. The α-TeO2 piezopotential will not be canceled out even if the microwires' tips are pointed towards each other according to the unique triangular morphology and its physical properties. The α-TeO2 triangular microwires can be used as a useful active sensor.

Optoelectronic Materials and Sensor Materials

We are the first to use a simple direct ultraviolet (UV, λ=380 nm) light via the decomposition approach to fabricate ZnO nanowires on a flexible and transparent polyethylene terephthalate (PET) substrate using a zinc acetylacetonate hydrate precursor in ambient air.  The ZnO nanoparticles exhibited a remarkable photocurrent−dark current ratio of ∼80 900%, which was 8.5 times that of the ZnO nanowires. While ZnO nanowires possessed many surface properties such as oxygen vacancies and interstitial Zn, which acted as key components in the photoresponsive properties and formation processes. The ZnO nanowires also reveal excellent photocatalytic activities under the illumination of visible light. Our study discovered that water molecules played a critical role in the surface defect states, affecting the morphology and the photoresponsive properties of the ZnO nanoparticles and nanowires.

Piezotronic Strain Sensors

In noncentrosymmetric (NCS) oxide groups, ferroelectric perovskites containing lead (Pb) and Bismuth (Bi) exhibit high polarization and piezoelectric performance but high toxicity. Discovering lead-free-based materials such as ZnSnO3 has not been extensively investigated in piezoelectric sensors and actuators. We first studied ZnSnO3 nanowires/microwires represent piezopotential distribution along the c-axis is 86 V. Also, a gauge factor in the ZnSnO3 strain sensor is 3740, which is 19 times and three times higher than that of Si and ZnO nanowires (or carbon nanotubes), respectively.

Recent first/corresponding-author publications: 

1. ACS Nano 2012, 6, 5, 4369–4374 

2. ACS applied materials & interfaces 6 (16), 14286-14292 

3. Nano Energy 14, 102-110