Effects of Electron–Phonon Coupling and Spin–Spin Coupling on the Photoluminescence of Low-Dimensional Metal Halides

Abstract

Low-dimensional metal halides (LDMHs), as a derivative of three-dimensional lead halide perovskites, have attracted much attention because of their unique crystal structures and fascinating photonic properties. The simple synthesis and rich photonic properties of LDMHs make them striking candidates for the development of lighting, photodetectors, biological imaging, etc. Although many novel LDMHs have been achieved with strong electron–phonon coupling related to their self-trapped excitons (STEs) and excellent optical responses, transition-metal halides or doped halides have not been covered in regard to their rich spin characteristics. In this Perspective, we aim to deeply understand the role of electron–phonon coupling and STEs with magnetic coupling effects in regulating the optical properties of LDMHs and try to provide a novel way or a series of novel systems for the realization of next-generation high-performance luminescent materials with spin-coupling-involved photonics. Finally, an outlook toward potential challenges and applications of such ionic semiconducting LDMHs is also presented.

Bright Green Emission from Self-Trapped Excitons Triggered by Sb3+ Doping in Rb4CdCl6

“…39 Therefore, a large but appropriate S (value: from 10 to 40, blue dashed frame, Figure 3) indicates the easy formation of STEs, thus leading to strong STEs emission. 38 By FWHM with temperature, the S for Rb 4 CdCl 6 :0.1Sb 3+ is calculated to be 34.94, which is higher than many recent reported metal halides and comparable to Sb 3+ -doped allinorganic metal halides (Figure 3 and Figure S8a). 16,19,39−47 Additionally, Γ op that shows the electron−phonon interactions can be obtained by the Toyozawa equation (eq 2).…”

“…A high value of S will lead to the strong lattice vibration leading to the weak PL or PL quench; for instance, the weak emission of Cs 3 Bi 2 I 9 with an S of 79.5 . Therefore, a large but appropriate S (value: from 10 to 40, blue dashed frame, Figure ) indicates the easy formation of STEs, thus leading to strong STEs emission . By fitting FWHM with temperature, the S for Rb 4 CdCl 6 :0.1Sb 3+ is calculated to be 34.94, which is higher than many recent reported metal halides and comparable to Sb 3+ -doped all-inorganic metal halides (Figure and Figure S8a).…”

“…The S value is related to the possibility of the formation of STEs. A high value of S will lead to the strong lattice vibration leading to the weak PL or PL quench; for instance, the weak emission of Cs 3 Bi 2 I 9 with an S of 79.5 . Therefore, a large but appropriate S (value: from 10 to 40, blue dashed frame, Figure ) indicates the easy formation of STEs, thus leading to strong STEs emission .…”

Highly Efficient Broadband Green Emission of (TPA)CuCl2 Single Crystals: Understanding the Formation of Self-Trapped States

“…The power-dependent emission spectra of (TPA)­CuCl 2 were measured at RT (Figure S4), and the results show a linear relationship at different excitation powers, which excludes the green emission caused by permanent defects . Subsequently, the excitation spectra monitored at 490–530 nm show a similar feature (Figure S5a), and the normalized emission spectra excited at different emission wavelengths (250–290 nm) also exhibit an identical profile (Figure S5b), both of which demonstrate that the broadband emission stems from the relaxation of the same excited state. , Combined with previously reported Cu­(I)-based compounds with broadband emission, we can attribute the observed highly efficient green emission of (TPA)­CuCl 2 derives from STEs caused by lattice distortion and exciton–phonon interaction. , The CIE color coordinate of (TPA)­CuCl 2 is located at (0.17, 0.42), corresponding to green light emission (Figure b). The absorption spectrum of (TPA)­CuCl 2 powders is given in Figure c.…”

[PPh3H]2[SbCl5]: A Zero-Dimensional Hybrid Metal Halide with a Supramolecular Framework and Stable Dual-Band Emission

“…Recently, organic–inorganic metal halides (OIMHs) have captured tremendous attention due to their superior optical/electronic properties. , Three-dimensional lead and tin halide perovskites, due to their delocalized electronic structures with large Wannier-type excitons, , are superior light-harvesting materials. , By electronic dimensionality engineering, the faster formation and radiative recombination of the excitons have been realized in low-dimensional OIMHs, showing promising light emission property. − Among them, zero-dimensional (0D) OIMHs based on n s 2 ions (mainly Ge 2+ , Sn 2+ , Pb 2+ , Sb 3+ , Bi 3+ , and Te 4+ ) performing distinctive photoluminescence (PL) with broad emission and large Stokes shift are of particular interest. − …”