Higher efficiency solar cells are required to reduce solar array mass, stowed volume, and cost
for numerous commercial and military applications. Conventional solar cell made of thin-film
or crystal-Si (c-Si) or other thin films have limited conversion efficiency of 10 to 20% with
the cost of $3-$5/Wp. Current state-of-the-art crystalline multijunction solar cells are ~30 %
efficient with the cost of $30 to $40 /Wp. Increasing conversion efficiency of > 30% will
enable to reduce the cost < $1/Wp and useful for various power platforms supporting mobile
wireless, laptop, tent applications. Solar cell comprises with three dimensional blocks are
shown to be higher conversion-efficiency than standard flat-type solar cell. Incorporating
nano-scaled blocks in solar cell structures are shown to be increased performances due to (i)
increase of the surface area to volume ratio, (ii) brining the junction closer to the carrier
generation region which eliminate the carrier recombination , (iii) absorption of all incident
photon flux, and (iv) broadening the absorption spectrum. Our activities on next generation
high performance solar cells based on micro-nano scaled structures and various material
systems will be presented. Details fabrication process of micro-nano scaled solar cell friendly
to mass scale manufacturing will be also be described. We have achieved more than 20x
optical performance enhancement for the solar cell based on micro-scaled structures, than that of flat-type (standard) solar cell, fabricated on the same Si substrate and same process.
Simulation results showed that significant improvement in conversion efficiency more than
30% is possible for even c-Si solar cell based on the micro-nano scaled structures. Key issues
and challenges for bringing it to the manufacturing will be discussed.
Detectors (sensor) having detection capability ranging from visible to near-infrared region are
very much required for multi-color image sensor, necessary for next generation bio-medical,
bio-chem(ical), and security applications. The capability of using broadband detection in a
single sensor would help to receive real-time imaging not detectable using today's CCD or
CMOS sensor. We proposed a detector structure as a single sensor element (pixel) having the
detection capability ranging from visible to 1.7 μm, wavelengths requiring in bio-chem, biomedical
cell detection and security application. This invited paper has
two-fold objectives: (a)
provide a comprehensive overview of conventional photo detectors array (focal-plan array) and
their types, being used in today's imaging, and (b) introduce a development of multi-color
detector array (image sensor) which authors pioneered. The features of proposed multi-color
detector are simple structure, low-cost, high quantum efficiency, high sensitivity, and high
speed. Performance results so far attained will be presented along with its possible applications.
Multi-wavelength (a.k.a. broadband) photodetector having a detection capability ranging from near ultra-violet to infrared can be useful as a common detector for various applications such as optical communication and optical interconnects etc. The capability of using single detector in receiver system for optical communication covering both data and transport systems, not only makes the total system cost lower, but it also makes easier the system vendors to reduce the inventory. We proposed detector having the detection capability ranging from 350 nm to 2000 nm, wavelengths that covers all optical communication wavelengths application. This invited paper has two-fold objectives: (a) provide a comprehensive overview of conventional photo detectors and their types, being used in today's optical communication and (b) introduce a development of broadband photodetector which authors pioneered. The features of proposed broadband detector are simple structure, low-cost, high quantum efficiency, high sensitivity, and high speed. Performance results so far attained will be presented along with its possible applications.
A novel photonic band-gap (PBG) based nano-sensor is proposed for cell, biomolecule gas, chemical agents, or various industrial gas detections. The sensor consists of waveguide, made from periodically structured dielectrics forming PBG. This sensor is optimized with a fixed wavelength of light and fixed receptor for detecting specific biomolecule or cell. The absorption of cell or biomolecule causes the changes in refractive index, which thereby changes the optical intensity. The concentration of cell or biomolecule agent can be known from the changes in optical output. The proposed sensor can be very high sensitive and can able to detect the fixed cell in very smaller amount or biomolecule gas in several parts per billion. We will present the detailed simulation for various applications for example in clinical diagnostic system to measure the specific cell
or DNA, or in spectroscopy for measuring various biomolecule gases in the space. In addition, this proposed sensor is able to detect the contamination of the environment (e.g. viral germs), food (fungus) and agricultural products.
A novel photonic band-gap (PBG) based nano-sensor is proposed for biomolecule gas/chemical agents, and various industrial gas detections. The proposed sensor is based on the plannar waveguide formed by utilizing the PBG. Sensor structure is optimized for a fixed wavelength of light and fixed recpetor. Biomolecule gas adsorbed/interact with the receptor, cause changes in refractive index, which thereby reduces the output optical power. Type of gas and its density in the air can be known from the changes in output optical power, compared with no-gas (reference) adsorption. The proposed sensor can able to detect the fixed gas in several tens of parts-per-billion. We will present detailed simulation and the results of this proposed sensor for various biomolecule gas/chemical agents and also industrial gases. In addition to biomolecule gas/chemical agents detection, the proposed nano-sensor is also expected to be useful for various applications for example in clinical diagnostic system to measure the specific cell or DNA.