We are working on both the second and third generation of solar cell materials.

For thin film based solar cells, we are interested in the CuIn_xGa_1-xSe₂ (CIGS) system, the efficiency record achieved for which is 19.9% for 1 cm2 area lab cell by NREL. Several major challenges exist in the CIGS based devices including the compositional control during the deposition; the understanding of its electronic structure, defect configuration and grain boundaries; and achieving the high open circuit voltage to band gap (V_OC /Eg) value.

For nanostructure based solar energy conversion devices, we are interested in a variety of semiconducting nanostructures (including inorganic materials as well organic/inorganic hybrid systems) as the light harvesting material, and exploring various novel device configurations for high efficiency and low cost PV solar cells as well as PEC cells. For example, using ZnO nanowire arrays on conducting substrate as the transparent conducting oxide, and semiconductor quantum dots as the light absorber would serve as one possible basic structure of photoelectrode.

a) SiO2 nanoparticles b)particles in Cell

In this project, we are interested in both cytotoxicity of nanoparticles and developing functionalized nanoparticulate systems for cancer therapies.

On the one hand, materials that are not toxic in the bulk form could be harmful to the cell at nanometer scale. We are interested in finding out how the nanoparticle's cytocoxicity changing with their size, shape, crystallinity and surface modification.

On the other hand, the specific magnetic/optical/electrical properties of nanoparticles not only provide novel means for tumor cell recognition, target delivery and effective treatment, but also make them effective biomarkers for tracing the drug delivery process, serving as feed-back massagers for identifying the mechanisms of drug uptake, functioning, and metabolism at the molecular and cellular level. Design and synthesis of nanostructured particles with controllable size and desired physical properties, functionalization of the particle surface, identification of the interaction between nanoparticles and cancer cells, as well as investigating the physiologic impact of nanoparticles to normal and cancer cells such as apoptosis and mutagenesis, will be the main focus of this project. Through integrated physical property measurements and biological evaluation of the nanoparticles, we will find out their delivery and functioning mechanisms in human cells, and also evaluate the efficacy of these nano-medicines

(a): Spatially resolved EELS and (b): momentum transfer
(q)dependent EELS of individual H2Ti3O7 nanotube

When fast electrons are scattered by a piece of solid, they will transfer certain amount of energy to the solid, which process has a direct correlation with the electronic structure and the dielectric property of that specific material. This technique is known as electron energy loss spectroscopy. With the recent hardware advances in transmission electron microscope and the energy loss spectrometer, it is now feasible to study materials with excellent spatial resolution (~1nm), so that the local electronic structures and dielectric properties of individual nanostructures can be explored.

Available Projects

-- Surface and interface plasmon of individual and interacting nanoparticles.

-- Momentum transfer dependent electronic structure of electronic materials

-- Electron magnetic chiral dichroism (EMCD) study of transition metal doped semiconducting nanostructures