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

Eline M. Hutter; María C. Gélvez-Rueda; Anna Osherov; Vladimir Bulović; Ferdinand C. Grozema; Samuel D. Stranks; Tom J. Savenije

doi:10.1038/nmat4765

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

Eline M. Hutter, María C. Gélvez-Rueda, Anna Osherov, Vladimir Bulović, Ferdinand C. Grozema, Samuel D. Stranks, Tom J. Savenije^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › Academic › peer-review

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.

Original language	English
Pages (from-to)	115-120
Number of pages	6
Journal	Nature Materials
Volume	16
Issue number	1
DOIs	https://doi.org/10.1038/nmat4765
Publication status	Published - 1 Jan 2017
Externally published	Yes

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title = "Direct-indirect character of the bandgap in methylammonium lead iodide perovskite",

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.",

author = "Hutter, {Eline M.} and G{\'e}lvez-Rueda, {Mar{\'i}a C.} and Anna Osherov and Vladimir Bulovi{\'c} and Grozema, {Ferdinand C.} and Stranks, {Samuel D.} and Savenije, {Tom J.}",

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AU - Hutter, Eline M.

AU - Gélvez-Rueda, María C.

AU - Osherov, Anna

AU - Bulović, Vladimir

AU - Grozema, Ferdinand C.

AU - Stranks, Samuel D.

AU - Savenije, Tom J.

PY - 2017/1/1

Y1 - 2017/1/1

N2 - 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.

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

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