PRISM SPECIAL SEMINAR: Metal Halide Perovskites for Photovoltaic Applications

Dec 2, 2021, 12:30 pm1:30 pm
Bowen Hall Auditorium 222



Event Description

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Abstract: Organic-inorganic metal halide perovskites have emerged as attractive materials for solar cells with power-conversion efficiencies now exceeding 25%. This seminar will provide an overview of our work unravelling the fundamental processes that have enabled these materials to be such efficient light-harvesters and charge collectors. We further examine a range of remaining challenges and opportunities relating to material microstructure, ionic migration and toxicity.

We demonstrate that the intrinsic mobility of charge carriers is governed by their interactions with optical vibrations of the lead halide lattice (Fröhlich interactions)[1]. We reveal that bimolecular (band-to-band) recombination, which dominates the charge-carrier losses near the fundamental Shockley-Queisser efficiency limit of solar cells, is an inverse-absorption process following the principle of detailed balance.[2]  In addition, highly effective photon reabsorption is shown to be operational in lead halide perovskites, further boosting attainable power conversion efficiencies beyond the Shockley-Queisser limit.[3] Our analysis of intrinsic photophysical parameters opens the promise of targeted material design for solar energy harvesting, based on readily accessible parameters, such as band structure, phonon frequencies and the dielectric function.

We further examine how the optoelectronic properties of hybrid perovskites are governed by their nanostructure. We show that lead halide perovskites can exhibit intrinsic quantum confinement, apparent through surprising oscillatory features in the absorption spectrum.[4] Such materials may thus offer the sought-after target of bottom-up nanostructuring. In addition, we discuss our recent discovery[5] of the atomic-scale microstructure in lead halide perovskites, demonstrating coherent interfaces with precursor remnants, sharp interfaces between perovskite grains, and a surprisingly resilient nature of the lattice with respect to partial loss of the organic cation. Finally, we outline some of the remaining challenges in the field, relating to ionic migration and toxicity of lead. In the context of silicon-perovskite tandem cells, we discuss the peculiar mechanisms underlying detrimental halide segregation in mixed iodide-bromide lead perovskites with desirable electronic band gaps near 1.75eV.[6]  We further outline the challenges and rewards of lead-free metal halide perovskites and their structural derivatives.

[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 7, 11755 (2016)

[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 9, 293 (2018)

[3] S. G. Motti, T. Crothers, R. Yang, Y. Cao, R. Li, M. B. Johnston, J. Wang, and L. M. Herz, 
Nano Letters 19, 3953 (2019).

[4] A. D. Wright, G. Volonakis, J. Borchert, C. L. Davies, F. Giustino, M. B. Johnston, and L. M. Herz, 
Nature Materials 19, 1201 (2020).

[5] M. U. Rothmann, J. S. Kim, J. Borchert, K. B. Lohmann, C. M. O’Leary, A. A. Sheader, L. Clark, H. J. Snaith, M. B. Johnston, P. D. Nellist, and L. M. Herz, Science 370, eabb5940 (2020).

[6] A. J. Knight, J. Borchert, R. D. J. Oliver, J. B. Patel, P. G. Radaelli, H. J. Snaith, M. B. Johnston, and L. M. Herz, 
ACS Energy Letters 6, 799 (2021).