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Center for Nonlinear Studies |
The low-cost technologies and the ease of synthesis of the Hybrid Organic Perovskites (HOP) raised up the interest in the field of optoelectronics [1] and solar cells [2]. Indeed 3D HOPs, lead to a novel class of low-cost materials for high efficiency hybrid semiconductor photovoltaic cells. A giant spin-orbit coupling (SOC) overlooked until recently is important both for 2D and 3D lead-halide based HOPs [3]. The optical absorption is associated to transitions between the spin–orbit split-off conduction band and the valence band. Strain effects induce band splitting analyzed with a k.p Hamiltonian. The interplay of SOC and point symmetry breaking, leads to large dispersion splitting away from the critical point [3]. We show that the broad light-harvesting abilities of the 3D HOP, is a direct consequence of their intrinsic multi-bandgap and multi-valley nature. The enhancement of the optical absorption by the excitonic interaction, observed at low temperature, is simulated by solving the Bethe-Salpeter equation in the cubic reference phase [3]. A screening mechanism of the excitonic interaction at room temperature is proposed. These results are in good agreement with recent results reported on the transport properties of the 3D HOP [4].
[1] D.B. Mitzi et al, Science., 1995.
[2] J. Burschka et al, Nature, 2013. M. Liu et al Nature, 2013.
[3] J. Even, et al Phys. Rev. B 2012, J. Phys. Chem. Lett. 2013, Phys. Status Solidi RRL solar, 2014.
[4] S. D. Stranks, et al, Science, 2013, G. Xing et al, Science, 2013.
Host: Sergei Tretiak