Alleviation of π–π* Transition Enabling Enhanced Luminescence in Emerging TpyInCl_x (x = 3, 5) Perovskite Single Crystals

Abstract

The general formula of perovskites can be written as A n BX 2+n , where A is monovalent cation like MA + (CH 3 NH 3 + ), [7] FA + ( + HC(NH 2 ) 2 ), [8] GA + ( + C(NH 2 ) 3 ), [9] and so forth, B is a divalent metal, usually Pb 2+ or Sn 2+ , and X is a halogen anion or hybrid halogen anions. When n = 1, the dimension of the perovskite is 3D, as we insert a larger organic group in A site, the structure dimension of perovskite is thereby transformed to 2D, 1D, or even 0D, which enables to enhance the structural stability against the humidity, and also realize the quantum self-trapped effect toward high photoluminescence quantum yield (PLQY). [10,11] For the displaying application, not only the high PLQY is required, but color-tunable emission is also a necessary characteristic, [12,13] which is generally realized through ion doping and/or substitution, such as Cs 4−x A x Sn(Br 1−y I y ) 6 [14] (A = Rb, K; x ≤ 1, y ≤ 1), Cs 2 AgIn x Fe 1−x Cl 6[15](0 ≤ x ≤ 1), PEA 2 (Rb x Cs 1−x ) n−1 Pb n (Br 1−y Cl y ) 3n+1 , [16] etc. Additionally, dimension regulation is also an effective way to control emission wavelength, e.g.

High-efficiency red photoluminescence achieved by antimony doping in organic–inorganic halide (C11H24N2)2[InBr6][InBr4]

“…22 Among these 0D broadband emissive metal halides, Inbased OIMHs have been found to be promising luminescent materials for solid-state lighting. [23][24][25][26][27][28][29][30][31] Chen et al synthesized 0D (C 7 H 10 N) 3 InBr 6 with isolated [InBr 6 ] 3À octahedra in the structure, which shows orange light emission with a relatively high PLQY of B35%. 23 4 ÁCl in which the yellow emission can be largely enhanced with the PLQY being boosted from 20% to 90% via Sb doping.…”

“…25 A DMF (N,N-dimethylformamide) sensor was also fabricated using this InCl 6 (C 4 H 10 SN) 4 ÁCl:Sb 3+ system based on its reversible luminescent vapochromism. 25 Blue emission contributed from the organic ligands can also be realized in (C 14 H 22 N)InBr 4 (PLQY = 16.36%) and TpyInCl 5 (PLQY = 47.66%; Tpy = 2,2 0 :6 0 ,2 00 -terpyridine), 26,29 and by combining the emission from the inorganic and organic ligands, the single-component white-light emission can also be achieved. 24,27 Very recently, strong green emission has also been realized in Inbased [DAPEDA]InCl 7 H 2 O and [DPA] 3 InCl 6 , and a high PLQY (89.2%) was also obtained after Sb doping (DAPEDA = 1,2-bis(3aminopropylamino)ethane, DPA = dipropylamine).…”

“…Among these 0D broadband emissive metal halides, In-based OIMHs have been found to be promising luminescent materials for solid-state lighting. 23–31 Chen et al synthesized 0D (C 7 H 10 N) 3 InBr 6 with isolated [InBr 6 ] 3− octahedra in the structure, which shows orange light emission with a relatively high PLQY of ∼35%. 23 Wei et al have described the bright yellow emissive (C 10 H 28 N 4 )In 2− x Sb 2 x Cl 10 with dimeric [In(Sb) 2 Cl 10 ] 4− inorganic units and a PLQY that can reach almost 100% by adjusting the In/Sb ratio.…”

0D hybrid indium halides with highly efficient intrinsic broadband light emissions

“…S14a (ESI†), the calculated band structures give theoretical band gaps of 4.188 eV and 2.918 eV for DMP-Cl and DMP-Br , respectively, which are slightly lower than the values obtained from the UV-vis absorption spectra due to the limitation of DFT theory (4.49 and 3.25 eV). 18 Both the valence and conduction bands display negligible dispersion, demonstrating the absence of electronic interactions between adjacent [InX 6 ] 3− octahedra. From the density of states, the valence band maximum (VBM) and conduction band minimum (CBM) are mainly contributed by the Cl-3p (Br-4p) and In-5s orbitals from the anionic [InX 6 ] 3− species, respectively.…”

“…Therefore, the excitons should be localized on the [InX 6 ] 3− units and the broadband light emission stems from STEs due to strong electron–phonon coupling in the soft crystal lattice. 13,15–20…”