Device Group
Surface Analysis Group
Art in Science
Device Group
- Hybrid Organic/Si Heterojunction Solar Cells
Hybrid Organic/Si Heterojunction solar cells take the concept of induced junction or heterojunction device wherein layers of organics is deposited on a crystalline substrate resulting in increased passivation and band-bending at the crystal surface. These hybrid cells hold great promise since they take advantage of both the high efficiency and reliability of Si, and the low material cost of organics. Our studies focused on electrical surface passivation, device fabrication and characterization.
At the same time, this project aims to develop a means of testing for defects in industrial multicrystalline wafers before they undergo subsequent processing steps into completed solar cells, which reduce costs by identifying underperforming wafers at an early point in the manufacturing process.
- Antireflection Coatings in III-V Solar Cells (Collaborated with Australia Researchers)
There are many avenues to improve the efficiency of III-V multijunction solar cells. Applying subwavelength structured Antireflection Coatings(ARCs) on the top of solar cells is among one of them. This project is aimed to use patterned ARCs to approach the Lambertian limits of cells over a broad wavelength.
- An investigation of the valence regions of Cu(In,Ga)Se2 and its alloys
Thin film PV is recognized as a pathway to meeting the goals of readily scalable, low cost PV which can be scaled-up into large volume manufacturing. However, for thin film PV to meet the strategic goals for transformative energy, higher efficiency and very low cost manufacturing approaches are needed. These needs are addressed by the development of tandem solar cells using Cu(InGa)Se2 technology, which already has demonstrated the highest efficiency thin film performance with single junction technology, and validation of high rate manufacturing approaches. The project on Cu(InGa)Se2 and tandem manufacturing addresses technology advancement barriers for improved performance and manufacturability by using novel (AgCu)(InGa)Se2 alloys to develop the wide bandgap solar cells needed for successful implementation of tandem solar cell concepts.
In this work, ultraviolet photoelectron spectroscopy was used to investigate the valence regions of Cu(In,Ga)Se2 alloyed with Ag. With increasing Ag concentration, we were able to show that the valence band maxima decreases to lower binding energies relative to the Fermi level, which indicates that the band gap of this semiconductor widens as the Ag concentration increases. Also, the anti-bonding feature from the p-d hybridization effect of Cu3d and Se4p orbitals shows a decrease in intensity when Ag% > Cu%. Indicative that less p-d hybridization is occurring when Ag% > Cu%.
Surface Analysis Group
- Atomic Layer Etching
Like widely used atomic layer deposition method, Atomic layer etching is a process that etch a thin film cycle by cycle with different gases. Comparing with continual plasma etching process, this method will have more precisely control in the process.
This project is cooperated with DRTC, Air Liquide. We are looking for suitable atomic layer etching condition for some materials like metals, which is used in electronic industry but hard to be etched. Our group focuses on the surface analysis of the etching performance, including XPS, AES, SEM, EDS, AFM; and mechanism study.
- Next Generation High-k’s
High-k’s are a class of material with a large dielectric constant most often exploited for their insulative electrical properties. They are often found in the incredibly thin gate layer of transistors. The industry standard since the 1960’s has been SiO2, but it has been known for some time that it will need to be replaced with another material due to some of it’s limitations. Our group has looked at a number of high-k oxides such as: HfO2, ZrO2, Nb2O5.
Art in Science
- Preservation of iconic early 20th century works
Preservationists and museum curators have looked to science for solutions to protect the most famous paintings in this era. For example, Henri Matisse’s famous “Le Bonheur de Vivre” or “Joy of Life” painting is demonstrating the telltale signs of photo-degradation in some of it’s yellow pigments. Chemical and elemental analyses point to yellows made from CdS as the ones that are deteriorating. Given the high profile and priceless value of these paintings, incredibly sensitive, high resolution characterization techniques are requisite to a successful partnership between Art and Science.
