Our research focuses on interdisciplinary topics of organic electronics, including surface and interface analysis, materials sciences, optoelectronics, renewable energy and device physics. The on-going research activities in the group include:
- Light trapping in organic heterojunction solar cells
This project is aimed at investigating and realizing high efficiency multilayer organic heterojunction solar cells through plasmon-enhanced optical absorption. The metal nanoparticles have a notable effect on the improvement of light absorption resulting in overall device performance. In order to take full advantages of the plasmonic enhancement in the light absorption in heterojunction organic solar cells, an in-depth investigation and optimization of plasmon-enhanced light absorption using metal nanoscale features in organic solar cells will be studied. This would enable effective utilization of both low-dimensional semiconductor structures and thin films of functional organic photoactive semiconductors, which have poor charge transport properties, for high performance solar cells. The improvement in device efficiency with the incorporation of metal nanoparticles will be investigated.
W. L. Barnes, A. Dereux, and T. W. Ebbesen, Nature 424, 824-830 (2003).
H. A. Atwater and A. Polman, Nat. Materials, 9, 205-213 (2010).
H. Shen, P. Bienstman, and B. Maes, J. Appl. Phys. 106, 073109, (2009).
P. Kulkarni, K. M. Noone, K. Munechika, S. R. Guyer, and D. S. Ginger, Nano Lett. 10, 1501-1505 (2010).
- Organic sensors
The sensors based on integrated organic light transmissible devices, such as organic photodetector (OPD) and OLEDs, provide the functional superiority for a broad range of applications. In this device architecture, the light absorption in OPD is carried out through the organic electroluminescent device which is transparent in visible wavelength. This integrated device uses OLED as a light source for illumination of the coupled OPD to create an optical signal. Such an integrated organic optoelectronic device can be a building block for sensors and has potential for application in monitoring systems. The design and fabrication flexibility provided by the organic semiconductors and processes also have significant cost benefit, making it possible for new application in organic electronics including imaging sensors, biological sensors, chemical sensors, position sensors, optical detectors, optical switches and other flexible electronic devices.
M. Ramuz, L. Bürgi, R. Stanley and C. Winnewisser, J. Appl. Phys. 105, (2009) 084508.
Y.Y. Lin, C. Cheng, H.H. Liao, S.F. Horng, H.F. Meng and C.S. Hsu, Appl. Phys. Lett. 89 (2006) 063501.
Y. Ohmori, H. Kajii, M. Kanedo, K.Yoshino, M. Ozaki, A. Fujii, M. Hikita, H. Takenaka and T.Taneda, IEEE J. Sel. Top. Quant. 10 (2004) 70.
- Study of novel transparent white-light OLED for Lighting
The aim of this project is to develop high performance transparent white-light OLED (WOLED) for illumination application. The WOLED is transparent when it is powered off or on. The new transparent WOLED structures enable a lighting device to produce a pleasant diffused light from both sides of the OLED and thus make possible new device concepts. The research work will be focusing on a p-i-n type phosphorescent-based transparent WOLED, a good understanding of charge injection and hole-electron current balance, light out-coupling structure to improve light extraction efficiency from both sides of transparent WOLED, and demonstrating transparent WOLEDs with a high optical transparency, color rendering index, high a power efficiency and device lifetime for application in novel lighting devices.
C. W. Law, K. M. Lau, M. K. Fung, M. Y. Chan, F. L. Wong, C. S. Lee and S. T. Lee, Appl. Phys. Lett. 89, 133511 (2006).
S.White, D.C.Olson, S.E.Shaheen, N.Kopidakis and D.S.Ginley, Appl.Phys.Lett. 89, 143517 (2006).
G. Dennler H. J. Prall, R. Koeppe, M. Eggiger, R. Autengruber and N. S. Sariciftci, Appl. Phys. Lett. 89, 073502 (2006).
F.X. Wang, T.Xiong, X.F. Qiao and D.G.Ma, Org. Electron., 10, 266 (2009).
- Transparent oxide semiconductors and application
Property doped transparent conducting oxides (TCOs) like ZnO, SnO2 and In2O3 are used individually or in separate layers or as mixtures such as indium tin oxide (ITO) and indium zinc oxide (IZO) for making oxide semiconductors. TCO films are fabricated by vacuum deposition methods such as rf/dc magnetron sputtering, and ITO electrodes, for example, are often patterned to form different contacts in devices. The patterning process usually involves the lengthy photolithographic steps, which is a time consuming and also is a wasteful process as only a small fraction of the ITO material actually ends up on the substrate. The rapid growth in production of large area flat panel displays including touch panel, organic light-emitting displays has led to a doubling in demand for ITO materials. There creates a need for depositing ITO and its alternatives more effectively and economically. In this project, we aim to develop high performance TCO films using dispersions with oxide nanoparticles. A deeper understanding of the relationships between the structure and the electro-optical properties of these materials will be the focus.
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G. M. Ng, E.L. Kietzke, T. Kietzke, L.W. Tan, P.K. Liew and F.R.Zhu, Appl.Phys.Lett. 90 (2007) 103505.