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Light-Conversion Mechanisms in Metal Halide Perovskites for Photovoltaics

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Organic-inorganic metal halide perovskites have emerged as attractive materials for solar cells with power-conversion efficiencies now exceeding 22%. We discuss the fundamental processes that have enabled these materials to be such efficient light-harvesters and charge collectors. We demonstrate that at the intrinsic limit, the mobility of charge-carriers is predominantly governed by interaction of carriers with optical vibrations of the lead halide lattice (Fröhlich interaction)[1]. In the absence of trap-mediated charge recombination, bimolecular (band-to-band) recombination will dominate the charge-carrier losses near the Shockley-Queisser limit. We show that in methylammonium lead triiodide perovskite, such processes can be fully explained as the inverse of absorption,[2] and exhibit a dynamic that is heavily influences by photon reabsorption inside the material.[3] Therefore, predictions of intrinsic charge-carrier mobilities and recombination rates can be readily made from easily accessible parameters, such as photon absorption spectra, phonon frequencies and the dielectric function, which allows for a targeted design of new materials for solar energy harvesting. Finally, we examine the prospect of such highly performing hybrid lead iodide perovskites in solar concentrator environments.[4] We demonstrate that in the absence of degradation, perovskite solar cells can exhibit appreciably higher energy-conversion efficiencies under solar concentration, where they should be able to exceed the Shockley-Queisser limit and exhibit strongly elevated open-circuit voltages.[4,5] [1] A.D. Wright, C. Verdi, R.L. Milot, G. E. Eperon, M. A. Pérez-Osorio, H. J. Snaith, F. Giustino, M. B. Johnston, L. M. Herz, Nature Communications 2016, 7, 11755 [2] C. L. Davies, M. R. Filip, J. B. Patel, T. W. Crothers, C. Verdi, A. D. Wright, R. L. Milot, F. Giustino, M. B. Johnston, L. M. Herz, Nature Communications 2018, 9, 293 [3] T. W. Crothers, R. L. Milot, J. B. Patel, E. S. Parrott, J. Schlipf, P. Müller-Buschbaum, M. B. Johnston, L. M. Herz, Nano Lett. 2017, 17, 5782 [4] Q. Lin, Z. Wang, H. J. Snaith, M. B. Johnston, L. M. Herz, Advanced Science 2018, 5 1700792 [5] Z. Wang, Q. Lin, B. Wenger, M. G. Christoforo, Y. H. Lin, M. T. Klug, M. B. Johnston, L. M. Herz, H. J. Snaith, Nature Energy 2018, DOI : 10.1038/s41560-018-0220-2

This talk is part of the Optoelectronics Group series.

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