Polarizable Anionic Sublattices Can Screen Molecular Dipoles in Noncentrosymmetric Inorganic–Organic Hybrids

Abstract

We report the growth and photophysical characterization of two polar hybrid lead halide phases, methylenedianiline lead iodide and bromide, (MDA)Pb2I6 and (MDA)Pb2Br6, respectively. The phases crystallize in noncentrosymmetric space group Fdd2, which produces a highly oriented molecular dipole moment that gives rise to second harmonic generation (SHG) upon excitation at 1064 nm. While both compositions are isostructural, the size dependence of the SHG signal suggests that the bromide exhibits a stronger phase-matching response whereas the iodide exhibits a significantly weaker non-phase-matching signal. Similarly, fluorescence from (MDA)Pb2Br6 is observed around 630 nm below 75 K whereas only very weak luminescence from (MDA)Pb2I6 can be seen. We attribute the contrasting optical properties to differences in the character of the halide sublattice and postulate that the increased polarizability of the iodide ions acts to screen the local dipole moment, effectively reducing the local electric field in the crystals.

Hot Carrier Cooling Mediated Efficiency Enhancement in Diamine Passivated Perovskite Solar Cells

“…MDA was chosen as an additive because its aromatic amines are π-conjugated molecules with efficient delocalized πelectrons, 26 which can move freely within the extended molecular orbitals, resulting in a more stable system with lower overall energy. Moreover, π−π interactions between organic spacers crystallize in a chevron-like pattern, 27 enhancing the structural rigidity. 28 Additionally, spacer cations with (NH 3 + -R-NH 3 + ) diammoniums eliminate van der Waals interactions, resulting in increased vertical charge conduction.…”

Influence of O−H⋅⋅⋅Pt interactions on photoluminescent response in the (Et4N)2{[Pt(bph)(CN)2][phenylene‐1,4‐diresorcinol]} framework

“…For example, cations or dedicated cation pairs are used for tuning the stability of hybrid metal halides and optical properties inherent in the metal halide skeleton via conditioning inorganic subnetwork dimensionality and topology, lattice or local symmetry, van der Waals separation and overall nanospace for electronic interaction. [1][2][3][4][5][6] In parallel, non-covalently bonded organic-inorganic systems (salts, double salts, co-crystal salts and solvates) involving functional discrete d-metallate complexes (polycyanidometallates, [7][8][9][10][11][12][13][14][15] polyoxometallates, [16][17][18] polyhalidometallates, [6,19] etc.) emerged to offer switchable dielectric properties, [7,8,10,12] piezo-and ferroelectric properties, [9] charge transfer (CT) and/or photoinduced electron transfer (PET) phenomena, [6,14,16,17,19] as well as nonlinear optical effects, [12] photoluminescence (PL) [12,17] and molecular waveguides functions.…”

Nonlinear and Emissive {[MIII(CN)6]3–···Polyresorcinol} (M = Fe, Co, Cr) Cocrystals Exhibiting an Ultralow Frequency Raman Response

“…This process relies on the interaction between matter and the incident beam, specifically, its polarization and orientation. The advantage of SHG lies in its narrow operating band, which allows for the precise control and manipulation of the generated signal. , The SHG function in the solid state requires a noncentrosymmetric space group and proper light absorption cutoff, which stimulated extended studies on the relevant inorganic, , organic, − as well as hybrid inorganic–organic − phases. In particular, the two latter composition strategies have recently been employed within the cocrystallization approach , considering the tunable intrinsic features of organic counterparts, e.g .…”