Electronic
Devices and
Materials
-Exploring
Future
Photovoltaic Devices and Sensors-
Welcome to visit my group home page! It is a
rewarding career
in my research group. My current research focuses on studies of
low-cost and high efficiency photovoltaic devices utilizing novel
nanoscale materials. One of the examples is the emerging perovskite
materials. Our group has long experience in fabrication and
characterization of semiconductor devices and sensors using novel
nanoscale materials. The graduates in my
research
area are highly demanded in industry (See Group Member Page). I always
need
outstanding people! Please feel free to send me
your
resume.
Dr. Chen's Research
Accomplishment
Google Scholar
Citation:
http://scholar.google.com/citations?user=lW-EfMYAAAAJ&hl=en&oi=ao
TiO2
Nanotubes and Carbon Nanotubes.
Dr.
Chen
had extensive experience in anodization of
aluminum when he
worked on humidity sensors in 1989-1992. In 2001, working with Dr. Dawei Gong, his postdoctoral
research
associate, and Prof. Craig A. Grimes who was then at Kentucky, he
successfully created TiO2
nanotubes through anodization of pure titanium,
a new type of inorganic oxide nanotubes. This idea came from his past
experience in humidity sensor research using anodization. As the corresponding author, Prof. Chen
first presented this work at Symposium Z3.9, 2001
MRS Fall Meeting, Nov. 26-29, 2001, Boston,
MA, USA.
The first author, Dr. Dawei Gong, moved with Prof.
Craig A. Grimes to Penn State
University, where the work was submitted to J. Mater. Res. with a wrong
address
of Prof. Chen, Wenchong Hu, and Suresh Singh. The paper entitled “Titanium
Oxide Nanotube Arrays Prepared By Anodic
Oxidation” was
published in J. Mater. Research 16, 3331-3334,
2001, Citation: >2,500 on
Google Scholar. In addition, he and
his co-workers fabricated the first vertically aligned carbon nanotube
(CNT)
arrays with high density and uniformity on silicon
substrates using porous anodic aluminum oxide (AAO) as templates (“Growth
of well-aligned carbon nanotube arrays on
silicon substrate using porous alumina film as nanotemplate”,
Appl.
Phys. Lett. vol.
79, 3083-3085, 2001, Citation: >170 on Google Scholar; “Ethylene
flame Synthesis of well-aligned multi-walled carbon nanotubes”, Chem.
Phys. Lett.
vol. 346, pp. 23-28, 2001, Citation:
>210 on Google Scholar ). This provides a
possibility for integration of carbon
nanotube arrays with silicon electronics. The above research has a
large impact
on nanoscale material research community.
Lithium
Doped TiO2 for Low-Cost
Perovskite Solar Cells. TiO2 is
both a dielectric material and a wide bandgap semiconductor. Dr. Chen
and his students developed Li-doped compact TiO2
layers used as electron transport layer in the planar heterojunction
perovskite solar cells and achieved the photo conversion efficiency
(PCE) of 17.1% with negligible hysteresis (Nano
Energy 31 (2017) 462–468) (Citations:
>150 on Google Scholars). Later he and his students found a
“stitching effect” of Isopropyl alcohol/Chlorobenzene mixed
anti-solvent in washing processes. This effect can be used to achieve
large grain sizes of perovskite films. Isopropyl alcohol molecules play
an important role in stitching cesium-containing triple cation
perovskite grains so that more homogeneous morphology and lower defect
density of perovskite films were achieved via this process. The solar
cells exhibited a stabilized PCE of 19.2% (Nano
Energy 39 (2017) 616–625) (Citations:
>110 on Google Scholars).
Novel
Humidity/Moisture Sensor. Dr.
Chen invented humidity/moisture
sensors based on alpha-alumina/silicon
dioxide
hybrid dielectric films. Unlike the regular humidity sensors,
moisture sensors with very high sensitivity
for sensing extremely low
moisture levels (<1 ppm) or dew point <-76 deg celsus are very
important for industrial processing and control. The worldwide market
for this type of sensors is over 1 billion dollars. The mainstream
moisture sensors used in dew point meters are porous gamma-phase
aluminum oxide. Unfortunately, gamma-phase aluminum oxide experiences
phase change from gamma phase to boemite. This phase change causes
calibration drift of moisture sensors. The commercial gamma-phase
aluminum oxide sensors have to be calibrated every six months. It is
well known that silicon dioxide is a very stable dielectric material.
Based on his experience in silicon dioxide research for MOS devices,
Dr. Chen invented alpha-alumina/silicon dioxide hybrid dielectric
moisture sensors, described in US Patent
8,739,623 (06/03/2014), US
Patent 9,285,334 (03/15/2016), and Chinese Invention Patent
201410246545 (08/24/2016). This novel sensor is being commercialized in
Advanced
Semiconductor Processing Technology LLC
(ASPT USA), Lexington, Kentucky, USA. In December 2014, ASPT LLC
secured $1M investment for product development and manufacturing scale
up. The novel humidity sensor has been featured in the Electrochemical
Society Interface Winter 2017 volume 26, issue 4, 67-70 (doi: 10.1149/2.F07174if). The products
are dew
point transmitters with three
types: T100, T80, T60. His
technical review about humidity sensors has made a large impact on
humidity sensor research community
(“Humidity
sensors: a review of materials and mechanisms”, Sensor
Letters vol. 3, 274-295, 2005，Citation:
>1180 on Google Scholar).
Hydgogen/Deuterium
(H/D)
Isotope Effect.
This effect was discovered
in 1996 by Drs. Lyding and Hess at
University of
Illinois at Urbana-Champaign (UIUC). As a graduate student at UIUC, Dr.
Chen helped develop this effect into
a
manufacturing process, so that integrated
circuits (microchips) lifetime is dramatically improved (IEEE Electron.
Dev.
Lett., vol. 19, pp. 444-446, 1998；IEEE
Electron. Dev. Lett., vol. 21, no. 5, 221-223, 2000). In addition, the
classical theory suggested that the hot-electron
degradation of MOS transistors was caused by hot electron injection
into the
gate insulator (SiO2). Based on his experiments
using H/D isotope effect, Dr. Chen
proved that it is not the hot-electron injection into the oxide but the
hot-electron
bombarding the SiO2/Si interface that causes the
degradation, (“On the mechanism for interface
trap generation in MOS transistors due to channel hot carrier stressing”,
IEEE
Electron. Dev. Lett., vol. 21, no. 1, 24-26, 2000). This laid a
foundation for
establishing a more accurate theoretical lifetime model for microchips,
which
is very important for the reliability of computers, cell phones, and
iPods/iPads etc.
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