Abstract
Zero-dimensional (0D) hybrid metal halides are under intensive investigation owing to their unique physical properties, such as the broadband emission from highly localized excitons that is promising for white-emitting lighting. However, fundamental understanding of emission variations and structure–property relationships is still limited. Here, by using pressure processing, we obtain robust exciton emission in 0D (C9NH20)6Pb3Br12 at room temperature that can survive to 80 GPa, the recorded highest value among all the hybrid metal halides. In situ experimental characterization and first-principles calculations reveal that the pressure-induced emission is mainly caused by the largely suppressed phonon-assisted nonradiative pathway. Lattice compression leads to phonon hardening, which considerably weakens the exciton–phonon interaction and thus enhances the emission. The robust emission is attributed to the unique structure of separated spring-like [Pb3Br12]6− trimers, which leads to the outstanding stability of the optically active inorganic units. Our findings not only reveal abnormally robust emission in a 0D metal halide, but also provide new insight into the design and optimization of local structures of trimers and oligomers in low-dimensional hybrid materials.
Highlights
INTRODUCTIONOrganic–inorganic hybrid metal halides are promising materials for use in advanced optoelectronics applications owing to their unique structural and physical properties, such as soft lattices, adjustable bandgap, and high absorption coefficient. Dimensionality engineering at molecular levels has been demonstrated to be an effective route for increasing the diversity of their architectures and improving their stability as the optically active inorganic clusters are tailored by hydrophobic cations. Recently, low-dimensional (lowD) metal halides have drawn great interest for their outstanding properties, including broadband emission from self-trapped excitons (STEs), potential high emission efficiency, and large Stokes shift. Especially for the zero-dimensional (0D) metal halides, near-unity photoluminescence quantum yield (PLQY) has been achieved by optimizing compositions and local structures. Current research focuses mainly on chemical tailoring, such as cation engineering, which is limited by tunability and may introduce a variety of influencing factors. A systematic understanding of how structure tuning affects optical properties is still lacking, and there is an urgent need for the development of advanced methods for regulation and in situ characterization
The emission is undetectable at ambient pressure, and a pressure-induced emission (PIE) centered at around 650 nm with a full width at half maximum (FWHM) of 175 nm can be observed at 1.6 GPa [inset in the left panel of Fig. 1(a)]
Pressure-induced emission has been revealed in the 0D hybrid metal halide6[Pb3Br12], with PL emerging at around 1.6 GPa and surviving to a record high pressure of 80 GPa among all kinds of hybrid metal halides
Summary
Organic–inorganic hybrid metal halides are promising materials for use in advanced optoelectronics applications owing to their unique structural and physical properties, such as soft lattices, adjustable bandgap, and high absorption coefficient. Dimensionality engineering at molecular levels has been demonstrated to be an effective route for increasing the diversity of their architectures and improving their stability as the optically active inorganic clusters are tailored by hydrophobic cations. Recently, low-dimensional (lowD) metal halides have drawn great interest for their outstanding properties, including broadband emission from self-trapped excitons (STEs), potential high emission efficiency, and large Stokes shift. Especially for the zero-dimensional (0D) metal halides, near-unity photoluminescence quantum yield (PLQY) has been achieved by optimizing compositions and local structures. Current research focuses mainly on chemical tailoring, such as cation engineering, which is limited by tunability and may introduce a variety of influencing factors. A systematic understanding of how structure tuning affects optical properties is still lacking, and there is an urgent need for the development of advanced methods for regulation and in situ characterization. We report pressure-induced, enhanced, and robust emission up to 80 GPa in a 0D hybrid metal halide (C9NH20)6Pb3Br12, hereinafter referred to as (bmpy)6[Pb3Br12] (where bmpy 1-butyl-1methylpyrrolidinium), which possesses linear [Pb3Br12]6− trimer clusters (face-sharing octahedra) isolated by organic cations.. Using pressure regulation in combination with in situ structural and optical characterization, we have systematically investigated pressuredependent photophysical properties. The emission of (bmpy)6[Pb3Br12] is still observable even at 80 GPa, which is the highest-recorded emission pressure for any kind of hybrid metal halide material. Such a robust emission is mainly due to the stiffness of the spring-like [Pb3Br12]6− trimers
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