The zero-dimensional perovskites composed of isolated polyhedrons have unique and distinct physical properties compared with threedimensional perovskites composed of interconnected polyhedrons. Here, we study the photodynamics of the zero-dimensional perovskite-like (C 6 H 22 N 4 Cl 3 )-SnCl 3 single crystals composed of isolated [SnCl 3 ] − tetrahedrons. They exhibit red luminescence with huge Stokes shift (2.49 eV), large spectral broadening (416 meV), and long lifetime (6.9 μs). The experiments in conjunction with the ab initio calculations reveal the special roles of high-and low-frequency phonons in the photodynamics of the (C 6 H 22 N 4 Cl 3 )SnCl 3 crystals. The resonance between the organic-cation-related high-frequency optical phonons and the singlet-totriplet state transition induces strong intersystem crossing and resultant spinforbidden luminescence. The strong electron−tetrahedron-related low-frequency optical-phonon coupling revealed by the low-temperature spectral characterization causes large spectral broadening. The strong lattice relaxation owing to localization of the electronic orbitals along with intersystem crossing accounts for the large Stokes shift.
The zero-dimensional (0D) metal halides
comprising isolated metal–halide
polyhedra are the smallest inorganic quantum systems and accommodate
quasi-localized Frenkel excitons with unique photophysics of broadband
luminescence, huge Stokes shift, and long lifetime. Little is known
about the role of polyhedron type in the characteristics of 0D metal
halides. We comparatively study three novel kinds of 0D hybrid tin
halides having identical organic groups. They are efficient light
emitters with a maximal quantum yield of 92.3%. Their most stable
phases are composed of octahedra for the bromide and iodide but disphenoids
for the chloride. They separately exhibit biexponential and monoexponential
luminescence decays due to different symmetries and electronic structures.
The chloride has the largest absorption and smallest emission photon
energies. A proposed model regarding unoccupied-energy-band degeneracy
explains well the experimental phenomena and reveals the crucial role
of polyhedron type in determining optical properties of the 0D tin
halides.
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