Embedded Files
RESEARCH INTERESTS
RESEARCH INTERESTS
1. Renewable energy devices including thin film solar cells and thermoelectricity
2. Printing fabrication of organic/inorganic devices
3. Device physics of inorganic/organic semiconducting devices
4. Study on the implementation of hybrid sensor system
5. Electronic modeling of devices by using Kelvin probe force microscopy (KPFM)
6. Development of instrumentation system for scientific and technical research
Development of airborne bio particle detection method
Development of airborne bio particle detection method
Since biological particles have UV-Light induced fluorescence characteristics, an optical method is widely used as a detection method, but due to the weak fluorescence intensity, many biological particle instruments use PMT to amplify weak signals. However, if it is intended to be used as a simple sensor in terms of personal health management, it is unrealistic to use PMT due to problems such as cost and size. This study is to obtain the total amount and size distribution of particles for all particles by using UV-LED and Photodiode and to detect the fluorescence amount of biological particles by introducing the “Spatio-temporal average method”. The goal is to develop a low-power, low-cost, small-sized biological particle sensing technology that can obtain information on the concentration and type distribution of biological particles in the air based on the correlation between the two.
○ Development of biological particle fluorescence detection sensor technology using UV-LED and Photodiode
○ Development of signal processing technology to improve the signal-to-noise ratio of microfluorescence signal detection
○ Flow simulation and optical/channel design considering signal processing response time
○ Establishment of particle size distribution and biological particle concentration prediction algorithm through scattering/fluorescence signal
<Fluorescence spectrum of the material to be measured (left), excitation-luminescence graph of components in milk (right)>
<Ray tracing simulation (left), fluorescence measurement structure cross-section (right)>
<Sensor structure design for flow simulation and flow in simulation>
<The spatiotemporal average sensing method of fluorescence>
[ Narrow focal point] (Left) [ Wide focal point ] (Right)
<Fluorescent measurement optical structure>
Gas sensing property of solution-processed graphene
Gas sensing property of solution-processed graphene
We fabricated the Graphene/PDMS composite with various weight concentration and the composite layers (0.5~40 wt%) made by spin-coating method. And then, we measured the impedance between the surface and the bottom of the layers. When any stress to the sample is applied, we found that it has only Reactance component. In other words, the sample surfaces are insulated. So, we assumed that the graphene sink down while fabricating the samples and the PDMS only
remains on the surface. To solve this problem, we added two steps to the fabrication process. The first is to spin coating with the partially cured composites that are put in a Desiccator without air access at room temperature (15°C) for 18 hours, and the second is curing at high temperature (~140℃) to cure the surface faster in the chamber compare to be cured on heat plate. After that we compared with samples by dielectric measurement.
Graphene(Gr) is interesting material for gas sensing devices. However, in processing method for making Gr(single or multi layers) requires special conditions, for example, CVD processing is required a vacuum condition. These things lead to high cost for making.
In this study, We made resistive finger type device by graphene dispersion solution in non vacuum and room temperature condition. We measured DC characteristics depending on various 𝐶𝑂2, 𝑁𝐻3 and relative humidity(RH).
Organic solar cell
Organic solar cell
Cross-sectional potential distribution of high open-circuit voltage bulk heterojunction photovoltaic device was measured using Kelvin probe force microscopy. Potential drop confined at cathode interface implies that photoactive layer is an effective p-type semiconductor. Potential values in field-free region show wide variation according to log-normal distribution. This potential dip prone to have holes captured during the diffusive motion, which can increase bimolecular recombination, while potential gradient in depletion region makes this potential dip smaller and the captured holes easily escape from dip region by Schottky barrier lowering. Keywords: BHJ device, Energy band diagram, Kelvin probe force microscopy
Google Sites
Report abuse