Electronic properties of polymers for photovoltaic applications

DIPC Seminars

Michel Côté, Univ. Montreal, Canada
Donostia International Physics Center (DIPC).Paseo Manuel de Lardizabal, 4 (nearby the Facultad de Quimica), Donostia
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Electronic properties of polymers for photovoltaic applications Organic photovoltaic devices are presently the subject of intense research since they could propose alternative solar energy solutions. Their main advantages are probably their reduced fabrication cost as compared to inorganic devices and the possibility to make flexible and light weight devices. Although devices made of organic materials such as polymers are not as efficient as inorganic semiconductors, their performance is increasing rapidly reaching presently close to 8%. The search for better photovoltaic polymers is very active, and ab initio calculations can help in this pursuit by assessing potential polymers and evaluate their value even before they are synthesized. Of the desirable properties, the band gap is surely crucial to improve efficiency and some candidate polymers that have better tuned optical properties to the solar spectrum will be presented. Another important issue for organic device is the electron transport material. Presently, electron transport is achieved with a fullerene derivative (PCBM) but this solution has some disadvantages. First, the ratio of PCBM to polymer has to be quite high to assure good electronic transport, and second, the relative high prize of PCBM is not compatible with the goal of reducing the cost of the device. For these reasons, a replacement for PCBM is desirable and an all polymer device solution is vie wed as the best avenue. An essential property for a polymer to be able to transport electrons is its electron affinity which has to be as high as possible. We will present results of calculations of polymers that meet this criterion. Also, we will discuss our efforts to address the problem of the energy levels in density-functional theory calculations.