1975: B.Sc. Hons, Physics/Imperial College, London

1979: Ph.D, Electronic Materials/ Imperial College, London

1980-1982: Spectrum Detectors Co. Ltd., London, UK Technical Director

1982-1990: Marconi Space System, Portsmouth, UK, Principal Egineer

1990-2005: Department of Physics, Hong Kong Baptist University, Associate Prof.

2005-present: Head, Department of Physics, Hong Kong Baptist University, Director, Centre for Advanced Luminescence Materials, Chair Prof.

Research interests:

1. Optical properties of silicon nano-structure.

2. Linear and non-linear optical properties of organic thin films.

3. Photonic nano-structures and photonic crystals.

Five-Photon up-conversion blue emission of a novel donor-π-accepter complex

Effective five photon absorption excited fluorescence stimulated with infrared femtosecond laser is reported in this work. The emission peak is located in the deep blue region. The square, cubic, biquadratic and five orders dependence of the fluorescence intensity versus pumping irradiance can be observed in the multi-photon absorption peaks.  The multi-photon absorption property is enhanced but without red shifting the emission wavelength and the quantum yield remains in  high value. Single bond of Calix-OPP(4)-SOR is used to enhance the polarization of the molecule and avoid the decrease in complanarity of π-conjugated plane. The molecular structures of the Calix-OPP(n)-SOR(n=1,4) (calix-1…-4)  have the general structure of D(donor)-π-A(acceptor). Intramolecular charge transfer from the terminal donor(decyloxy group), through the  π-bridge (olejophenylene) to the acceptor (alkylsulfonyl group). The multiphoton absorptivity can be controlled through the modification of molecular structure to influence the amount intramolecular charge transfer. The absorption cross-section, σ^TPA, is enhanced but without red shifting the emission wavelength and the quantum yield remains high.

1982: B.Sc. Hons, Chemistry, Hong Kong Baptist University

1992: Ph.D, Department of Chemistry, University of Texas at Austin, USA

1992-1997: Université Louis Pasteur, France and ETH-Zürich, Switzerland

1997-1998: Department of Chemistry, Australian National University, Australia, Visiting Fellow and The Laser Physics Centre, Research School of Physuics Sciences & Engineering, Australian National University, Australia, Research Fellow

1998-2007: Department of Chemistry, Hong Kong Baptist University, Assistant and Associate Prof.

2007-present: Department of Chemistry, Hong Kong Baptist University, Prof.

Research interests:

Design, synthesis and characterization of functional molecules for chemical sensors, photovoltaic effect, nonlinear optical response, light-emitting and liquid crystalline properties

Small Molecule Donor Materials for Organic Solar Cells

Organic/polymeric photovoltaic (PV) cells show promise as a low-cost, lightweight, flexible, and renewable energy sources and have been extensively investigated in the past decade. To further improve the efficiency of a heterojunction PV cell, the development of new p-type organic/polymer semiconductors that possess a broad and narrow absorption bandgap to harvest more solar radiation as well as a high charge mobility to transport the photogenerated charges to the electrodes is of paramount importance. Towards this end, we have recently synthesized novel series of narrow optical gap and hole-transporting functional oligothiophenes and dendritic oligothiophenes as a p-type semiconductor and investigated for photovoltaic applications. To reduce the absorption bandgap of a donor material, the donor-acceptor approach was employed. With the incorporation of hole-transporting diarylamino or carbazole moieties as an electron donating group conjugated with dicyanovinyl or tricyanovinyl electron withdrawing group, the optical energy gap of oligothiophenes greatly reduces to 1.91-1.46 eV and the first ionization energy remains high at ~5.1-5.2 eV. Various heterojunction PV cells have been fabricated from these materials and investigated. The device performance will be presented and discussed.

1983: B.Sc. Hons, Physics/Fudan University

1993: Ph.D, Charles Darwin University, Australia

1993-1995: Department of EEE, Kyoto University, Japan, Postdoctoral Fellow

1995-1997: Department of Physics, Murdoch University, Australia, Research Fellow

1998-2000: IMRE, Singapore, Research Scientist

2001-2009: IMRE, Singapore, Senior Scientist

2009-present: Department of Physics, Hong Kong Baptist University, Prof.

Research interests:

(1) Organic photovoltaics, OLEDs

(2) Thin film physics and surface science

(3) Physics of oxide semiconductor thin films and applications

Optical Enhancement in Organic Photovoltaic Devices

Compared to current silicon-based solar cells that are rigid, organic-based solar cells that use solution-based processing or low-cost non-vacuum deposition techniques are simpler and less expensive to manufacture. Organic photovoltaic cells can be made flexible, translucent and are light weight, offer more opportunities for application in new markets such as mobile electronics, disposable electronics, smart cards, digital applications, power generating windows, smart sensors, automotive, home appliances and outdoor lifestyle etc. An optical admittance analysis is used to study the optical enhancement in poly(3-hexylthiophene) (P3HT): 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM)-based organic photovoltaic cells. The results of this work have yielded a promising mean external quantum efficiency of ~ 45% and a power conversion efficiency of 1.7% for a semitransparent organic solar cell having a 75 nm thick polymer blend of P3HT:PCBM.The possible designs to improve the performance of semitransparent organic solar cells over the two competing indexes of power conversion efficiency and transmittance will be also discussed.