张渊博士
加州大学圣芭芭拉分校
报告时间：4月2日（周三）14:30
报告地点：科学楼902
Abstract
Conjugated polymers (CPs) are attractive materials which promise applications in energy conversion devices, large-area displays, and plastic electronics with low-cost fabrication. The functionalities and efficiencies of organic optoelectronics based on CPs are primarily dictated by the charge transport properties.
Molecular doping is a powerful strategy in mediating the charge transport in solution-processed CPs. By virtue of p-type doping, the hole mobility of CPs is enhanced with the background hole density controllable by doping levels. This allows for precisely control over the charge injection barrier to the semiconductor. By using a carrier-density dependent mobility model, one obtains a thorough description of the hole transport and temperature dependence in CPs upon doping. In contrast to the hole transport, electron transport in many CPs is trap-limited, giving rise to severe problems in related device applications. With molecular n-type doping, traps are deactivated, leading to trap-free and balanced electron and hole transport in organic diodes. Molecular doping has been strategically applied for polymer bulk heterojunction photovoltaics (BHJ-PVs), bilayer light-emitting diodes and transistors, showing universal application in realizing improved device performance.
In the second part of the talk, charge transport and recombination in organic solar cells based on solution-processed CPs and small molecules (SM) will be discussed. The recombination rate coefficient of SM BHJ-PVs exhibits stronger carrier density dependences than that of polymer P3HT:PCBM cells. These results enable in-depth understandings of the carrier losses and the irradiation intensity dependence of the BHJ-PV efficiency.
In the final part, strategies using DNA layers to tackle charge injection barriers in organic optoelectronics will be discussed. The key functionalities and mechanisms of the DNA layer are related to an interfacial dipole interaction. Latest results in applications of interfacial engineering using DNA layers in organic BHJ-PVs will be discussed.
个人简介：
I was born in Xi'an, China. I received my bachelor and master degree in condensed matter physics at Fudan University (China). I was awarded my Ph.D. in Physics at the Zernike Institute for Advanced Materials, University of Groningen (The Netherlands) in 2010. Since then I came to the Center for Polymers and Organic Solids (CPOS) at the University of California, Santa Barbara. My current research interest is on molecular semiconductors with a focus on charge carrier transport, injection, recombination and interfaces of optoelectronics, including organic solar cells, field-effect transistors and light-detectors. I have worked on molecular doping of conductive polymers and polymer light-emitting diodes. Before this I had worked on X-ray diffraction imaging using synchrotron radiation.