Photocurrent generation in printable organic photovoltaic cells
Printable photovoltaic materials including pi-conjugatyed organic materials and metal halide perovskites offer tremendous potential for low cost clean energy. However, the design of more effective materials is hindered by lack of understanding of the mechanisms by which these complex and disordered materials convert light to electricity. We have developed a series of time-resolved optical spectroscopy experiments that resolve different properties of photoexcitations in these materials. In this talk, I will review some of our recent insights from ultrafast spectroscopy. For organic photovoltaic materials, these highlights include evidence for ultrafast long-range charge separation,1 as well as the roles of delocalised excitons2 and disordered phases,3 singlet exciton fission,4 along with the remarkable rise of non-fullerene electron acceptors.5 The organic materials will be contrasted with efficient organometal halide perovskites, where we find efficient free charge photogeneration.6,7 These developments will unlock another step change improvement in photovoltaic cell efficiencies.
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2. K. Chen, A. J. Barker, M. E. Reish, K. C. Gordon, J. M. Hodgkiss J. Am. Chem. Soc. 2013, 135, 18502-18512.
3. J. K., Gallaher, S. K. K. Prasad, W. Lee, M. A. Uddin, J.-Y. Kim, H. Y. Woo, J. M. Hodgkiss, Energy Environ. Sci., 2015. 8, 2713-2724.
4. S. Lukman, A. J. Musser, K. Chen, S. Athanasopoulos, C. K. Yong, Z. Zeng, Q. Ye, C. Chi, J. M. Hodgkiss, J. Wu, R. H. Friend N. C. Greenham, Adv. Funct. Mat., 2015, 25, 5452–5461.
5. Lin, X, et al, Adv Mater 2017, 29, 1604155.
6. K. Chen, A. J. Barker, F. L. C. Morgan, J. E. Halpert, J. M. Hodgkiss J. Phys. Chem. Lett. 2015, 6, 153-158.
7. M. Price, J. Butkus, T. C. Jellicoe, A. Sadhanala, A. Briane, J. E. Halpert, K. Broch, J. M. Hodgkiss, R. H. Friend, F. Deschler Nature Comm. 2015. 6, 8420.