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Conjugated polymer chains have many degrees of conformational freedom and interact weakly with each other, resulting in complex microstructures in the solid state. Understanding charge transport in such systems, which have amorphous and ordered phases exhibiting varying degrees of order, has proved difficult owing to the contribution of electronic processes(More)
The increasing amount of research on solution-processable, organic donor-acceptor bulk heterojunction photovoltaic systems, based on blends of conjugated polymers and fullerenes has resulted in devices with an overall power-conversion efficiency of 6%. For the best devices, absorbed photon-to-electron quantum efficiencies approaching 100% have been shown.(More)
We examine the significance of hot exciton dissociation in two archetypical polymer-fullerene blend solar cells. Rather than evolving through a bound charge transfer state, hot processes are proposed to convert excitons directly into free charges. But we find that the internal quantum yields of carrier photogeneration are similar for both excitons and(More)
Interfaces between organic electron-donating (D) and electron-accepting (A) materials have the ability to generate charge carriers on illumination. Efficient organic solar cells require a high yield for this process, combined with a minimum of energy losses. Here, we investigate the role of the lowest energy emissive interfacial charge-transfer state (CT1)(More)
In this article we report the weak but omnipresent electroluminescence (EL) from several types of organic polymer:fullerene bulk heterojunction solar cells biased in the forward direction. The light emitted from blends of some commonly used polymers and the fullerene molecule is significantly different from that of any of the pure materials comprising the(More)
Dr. Y. Zhou, Dr. T. Kurosawa, Dr. L. Fang, Dr. Y. Diao, Dr. J. Reinspach, Dr. J. Mei, Dr. A. L. Appleton, Dr. G. I. Koleilat, Prof. Z. Bao Department of Chemical Engineering Stanford University Stanford , California 94305 , USA E-mail: zbao@stanford.edu Y. Guo, Dr. Q. Yan, Prof. D. Zhao College of Chemistry Peking University Beijing 100871 , China E-mail:(More)
In order to commercialize polymer solar cells, the fast initial performance losses present in many high efficiency materials will have to be managed. This burn-in degradation is caused by light-induced traps and its characteristics depend on which polymer is used. We show that the light-induced traps are in the bulk of the active layer and we find a direct(More)
Dr. K. Vandewal, Prof. M. D. McGehee, Prof. A. Salleo Department of materials science and engineering Stanford University Stanford , CA94305 , USA E-mail: koen.vandewal@iapp.de; asalleo@stanford.edu Dr. K. Vandewal, Dr. J. Widmer, Prof. K. Leo, Dr. M. Riede Institut für Angewandte Photophysik Technische Universität Dresden George-Bähr-Straße 1, 01069 ,(More)
The field dependence and yield of free charge carrier generation in polymer:fullerene blends with varying energetic offsets is not affected when the excitation energy is varied from above band-gap to direct CT state excitation. Instead, the ability of the CT state to split is dictated by the energetic offset between the relaxed CT state and the charge(More)
An N-Type organic thin-film transistor (OTFT) based on doped 6,13-Bis(triisopropylsilylethynyl)pentacene is presented. A transition from p-type to n-type occurrs with increasing doping concentrations, and the highest performing n-channel OTFTs are obtained with 50 mol% dopant. X-ray diffraction, scanning Auger microscopy, and secondary ionization mass(More)