Lecture:Design and synthesis of conjugated materials for solar cells
Speaker： Prof. Mats R. Andersson
Time： 10:00 a.m, Jun. 24 (Friday)
Venue： Meeting Room No. 01, New Building of the School of Materials Science and Engineering
Abstract:
Polymer solar cells have gained considerable interest during the last decades. The most promising active layer material comprises so-called bulk-heterojunction blends of a donor polymer that is finely mixed with a fullerene acceptor. The photovoltaic performance has increased rapidly over the last years with power conversion efficiencies now exceeding 11% for lab-scale single-junction devices. One advantage of polymer solar cells is the possibility to use roll-to-roll coating techniques for large-scale device production. However, several issues must be resolved before the efficiencies of lab-scale devices can be reproduced on large scale.
The development of high efficiency polymer solar cells is a challenging research task and our efforts have, during several years, been concentrated on synthesizing and evaluating new materials. Through the last years considerable effort has been put into decreasing the bandgap of the conjugated polymers with the objective to extend the absorption to longer wavelengths. Thereby, a larger part of the solar spectrum is covered. Introduction of donor-acceptor segments in the polymer backbone, creating internal push pull systems, is a method we have used to prepare a number of polymers with reduced bandgap.
Recently we synthesized a blue donor-acceptor copolymer called TQ-1, which in hero cells shows a maximum efficiency around 6%. This polymer simply consists of thiophenes alternating with substituted quinoxaline units and is easily synthesized in only a few steps. To increase the thermal stability of the active material different methods to stabilize the morphology will be described. In the search for new high performing polymers hero cells showing efficiencies above 7% will also be presented.
In our experience the interlayer materials that combine conjugated functionalities with amine derivatives give unstable modification of the electrode work function under ambient conditions, whereas stability is a prerequisite for a large scale roll-to-roll production process. Thus, it would be desirable to develop a method that permits to mitigate the poor stability of interlayer materials. In this work we establish that fullerene mixtures can be used to simultaneously achieve both interlayer modification of the cathode and improved thermal stability of a polymer:fullerene bulk-heterojunction blend.
Profiles:
Mats Andersson performed a joint PhD-work at the former Departments of Organic Chemistry and Polymer Technology at Chalmers University of Technology, Gothenburg, Sweden, and he received his PhD degree in Organic Chemistry in 1995. He spent one year as a post doctoral fellow at the Institute for Polymers and Organic Solids, University of California, Santa Barbara (UCSB), working in Prof. Alan Heegers group. Thereafter, he returned to Chalmers where he was appointed Professor in Polymer Chemistry in 2004 and he held a chair in Polymer Chemistry 2007-2015. Between 2008-2012, Mats was the head of the division of Applied Chemistry at the Department of Chemical and Biological Engineering, Chalmers University of Technology. In 2011 he received the Arrhenius medal from the Swedish Chemical Society and in 2012 he was elected as a member of the Royal Swedish Academy of Engineering Sciences, IVA. In 2014 Mats moved from Sweden to Adelaide to join UniSA and the Ian Wark Research Institute as a Research Professor. The institute was converted into the Future Industries Institute in 2015. He was awarded a South Australian Chair in Energy in 2014 and he is currently maintaining a close cooperation with Chalmers University of Technology.