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Issue 2, 2017
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Indirect to direct bandgap transition in methylammonium lead halide perovskite

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Abstract

Methylammonium lead iodide perovskites are considered direct bandgap semiconductors. Here we show that in fact they present a weakly indirect bandgap 60 meV below the direct bandgap transition. This is a consequence of spin–orbit coupling resulting in Rashba-splitting of the conduction band. The indirect nature of the bandgap explains the apparent contradiction of strong absorption and long charge carrier lifetime. Under hydrostatic pressure from ambient to 325 MPa, Rashba splitting is reduced due to a pressure induced reduction in local electric field around the Pb atom. The nature of the bandgap becomes increasingly more direct, resulting in five times faster charge carrier recombination, and a doubling of the radiative efficiency. At hydrostatic pressures above 325 MPa, MAPI undergoes a reversible phase transition resulting in a purely direct bandgap semiconductor. The pressure-induced changes suggest epitaxial and synthetic routes to higher efficiency optoelectronic devices.

Graphical abstract: Indirect to direct bandgap transition in methylammonium lead halide perovskite

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Publication details

The article was received on 22 Sep 2016, accepted on 09 Dec 2016 and first published on 09 Dec 2016


Article type: Communication
DOI: 10.1039/C6EE03474H
Citation: Energy Environ. Sci., 2017,10, 509-515
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    Indirect to direct bandgap transition in methylammonium lead halide perovskite

    T. Wang, B. Daiber, J. M. Frost, S. A. Mann, E. C. Garnett, A. Walsh and B. Ehrler, Energy Environ. Sci., 2017, 10, 509
    DOI: 10.1039/C6EE03474H

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