Direct-indirect character of the bandgap in methylammonium lead iodide perovskite

Journal article (2017)

Authors

E.M. Hutter ChemE/Opto-electronic Materials -

M.C. Gelvez Rueda ChemE/Opto-electronic Materials -

Anna Osherov Massachusetts Institute of Technology

Vladimir Bulović Massachusetts Institute of Technology

F.C. Grozema ChemE/Opto-electronic Materials -

Samuel D. Stranks Cavendish Laboratory, Massachusetts Institute of Technology

T.J. Savenije ChemE/Opto-electronic Materials -

Research Group

ChemE/Opto-electronic Materials () (TU Delft)

DOI: https://doi.org/10.1038/nmat4765

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Published Date

2017

Language

English

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Faculty

Applied Sciences

Department

ChemE/Chemical Engineering

Research Group

ChemE/Opto-electronic Materials

Abstract

Metal halide perovskites such as methylammonium lead iodide (CH₃ NH₃ PbI₃) are generating great excitement due to their outstanding optoelectronic properties, which lend them to application in high-efficiency solar cells and light-emission devices. However, there is currently debate over what drives the second-order electron-hole recombination in these materials. Here, we propose that the bandgap in CH₃ NH₃ PbI₃ has a direct-indirect character. Time-resolved photo-conductance measurements show that generation of free mobile charges is maximized for excitation energies just above the indirect bandgap. Furthermore, we find that second-order electron-hole recombination of photo-excited charges is retarded at lower temperature. These observations are consistent with a slow phonon-assisted recombination pathway via the indirect bandgap. Interestingly, in the low-temperature orthorhombic phase, fast quenching of mobile charges occurs independent of the temperature and photon excitation energy. Our work provides a new framework to understand the optoelectronic properties of metal halide perovskites and analyse spectroscopic data.

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