Origin of unusual bandgap shift and dual emission in organic-inorganic lead halide perovskites.
Emission characteristics of metal halide perovskites play a key role in the current widespread investigations into their potential uses in optoelectronics and photonics. However, a fundamental understanding of the molecular origin of the unusual blueshift of the bandgap and dual emission in perovskites is still lacking. In this direction, we investigated the extraordinary photoluminescence behavior of three representatives of this important class of photonic materials, that is, CH3NH3PbI3, CH3NH3PbBr3, and CH(NH2)2PbBr3, which emerged from our thorough studies of the effects of temperature on their bandgap and emission decay dynamics using time-integrated and time-resolved photoluminescence spectroscopy. The low-temperature (<100 K) photoluminescence of CH3NH3PbI3and CH3NH3PbBr3reveals two distinct emission peaks, whereas that of CH(NH2)2PbBr3shows a single emission peak. Furthermore, irrespective of perovskite composition, the bandgap exhibits an unusual blueshift by raising the temperature from 15 to 300 K. Density functional theory and classical molecular dynamics simulations allow for assigning the additional photoluminescence peak to the presence of molecularly disordered orthorhombic domains and also rationalize that the unusual blueshift of the bandgap with increasing temperature is due to the stabilization of the valence band maximum. Our findings provide new insights into the salient emission properties of perovskite materials, which define their performance in solar cells and light-emitting devices.
Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
M Ibrahim
MI
Dar
Laboratory of Quantum Optoelectronics, Institute of Physics, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
Gwénolé
G
Jacopin
Laboratory of Computational Chemistry and Biochemistry, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
Simone
0000-0002-3925-3799
S
Meloni
Istituto Officina dei Materiali, CNR-IOM SLACS Cagliari, Cittadella Universitaria, Monserrato (CA) 09042-I, Italy.
Alessandro
0000-0002-1381-6557
A
Mattoni
Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
Neha
N
Arora
Laboratory of Computational Chemistry and Biochemistry, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
Ariadni
A
Boziki
Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
Shaik Mohammed
SM
Zakeeruddin
Laboratory of Computational Chemistry and Biochemistry, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
Ursula
0000-0002-1704-8591
U
Rothlisberger
Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
Michael
M
Grätzel
Hybrid perovskites; density functional theory; luminescence; photoluminescence; photovoltaics