Understanding and controlling the relaxation process of optically excited charge carriers in solids with strong correlations is of great interest in the quest for new strategies to exploit solar energy. Usually, optically excited electrons in a solid thermalize rapidly on a femtosecond to picosecond timescale due to interactions with other electrons and phonons. New mechanisms to slow down thermalization would thus be of great significance for efficient light energy conversion, e.g. in photovoltaic devices. Ultrafast optical pump probe experiments in the manganite Pr0.65Ca0.35MnO3, a photovoltaic and electro-catalytic material with strong polaronic correlations, reveal an ultra-slow recombination dynamics on a nanosecond-time scale [1]. The photo-diffusion of excited electron-hole polaron pairs gives rice to a pronounced photovoltaic effect [1,2] and is studied by electron beam induced current (EBIC) on nanometer length scales [3]. Theoretical considerations suggest that the excited charge carriers are trapped in a hot polaron state. The dependence of the lifetime on charge order implies that strong correlation between the excited polaron and the octahedral dynamics of its environment appears to be substantial for stabilizing the hot polaron [4]. Furthermore, modification of the interfacial atomic and electronic structure of the manganite-titanite junctions gives insights into the processes underlying the transfer of a small polaron across the interface [5].

[1] Evolution of hot polaron states with a nanosecond lifetime in a manganite, D. Raiser, S. Mildner, B. Ifland, M. Sotoudeh, P. Blöchl, S. Techert, C. Jooss, Advanced Energy Materials, 2017, 1602174, DOI: 10.1002/aenm.201602174

[2] Polaron absorption for photovoltaic energy conversion in a manganite-titanate pn-heterojunction, G. Saucke, J. Norpoth, D. Su, Y. Zhu and Ch. Jooss, Phys. Rev. B 85, 165315 (2012).

[3]  Low energy scanning transmission electron beam induced current for nanoscale characterization of p-n junctions, Patrick Peretzki, B. Ifland, C. Jooss, M.Seibt, Phys. Status Solidi RRL 11,1600358 (2017)

[4] Contribution of Jahn-Teller and charge transfer excitations to the photovoltaic effect of manganite/titanite heterojunctions, B. Ifland, J. Hoffmann, B. Kressdorf, V. Roddatis, M. Seibt and Ch. Jooss, New Journal of Physics, 19 (2017) 063046

[5 ] Current–voltage characteristics of manganite–titanite perovskite junctions, B. Ifland, P. Peretzki, B. Kressdorf, Ph. Saring, A. Kelling, M. Seibt and Ch. Jooss, Beilstein Journal of Nanotechnology, 2015, 6, 1467–1484