Development of new conjugated polymers for solar cells

The impending energy crisis caused by the increasing demand for fossil fuels and rapidly vanishing fossil fuel reserves, coupled with the threat of climate change from rising carbon dioxide levels has put renewable energy firmly on the global agenda. One of the biggest challenges for scientists has become finding sustainable solutions to address the energy needs of the world, without causing adverse effects on the environment. Photovoltaic technologies, which can convert solar energy into electricity without causing harmful emissions, are one of the most attractive and viable technologies that fulfil this aim. At present, most of the available photovoltaic products are silicon-based solar cells. However, the high cost and pollution caused during the manufacture of silicon-based solar cells have limited their widespread application. Organic solar cells (OSCs) are one of the most promising applications for π-conjugated materials due to their potential to provide a green and cheap solution for the impending energy crisis.

                  The device architecture of OSCs are shown in the Figure a), in which the active layer is sandwiched between an anode and a cathode. The active layer is typically comprised of a polymer as a donor and a fullerene derivative (e.g. PCBM) as an acceptor. The donor and the acceptor materials are intimately blended to form interpenetrating bicontinuous networks, known as the bulk heterojunction (BHJ) structure as shown in Figure b). When light is absorbed by the active layer, coulombically bound electron and hole pairs, termed excitons, are generated, which diffuse to the donor/acceptor (D/A) interface where they dissociate. The electrons and holes can subsequently be efficiently transported to the electrodes.

                  The focus of this project is to develop new conjugated polymers, which can serve as the donor material for organic solar cells. Currently, the polymers we have developed can give power conversion efficiencies of up to 8%.


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Figure 1. a) Device architecture of solar cells. b) Bulk heterojunction structure of active layer of solar cells


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Figure 2. Chemical structure of an isoindigo polymer P3TI




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Published: Fri 06 Feb 2015. Modified: Tue 10 Feb 2015