Design, Structure, and Optical Properties of Organic−Inorganic Perovskites Containing an Oligothiophene Chromophore

Abstract

A quaterthiophene derivative, 5,5' "-bis(aminoethyl)-2,2':5',2' ':5' ',2' "-quaterthiophene (AEQT), has been selected for incorporation within the layered organic-inorganic perovskite structure. In addition to having an appropriate molecular shape and two tethering aminoethyl groups to bond to the inorganic framework, AEQT is also a dye and can influence the optical properties of lead(II) halide-based perovskites. Crystals of C(20)H(22)S(4)N(2)PbBr(4) were grown from a slowly cooled aqueous solution containing lead(II) bromide and quaterthiophene derivative (AEQT.2HBr) salts. The new layered perovskite adopts a monoclinic (C2/c) subcell with the lattice parameters a = 39.741(2) Å, b = 5.8420(3) Å, c = 11.5734(6) Å, beta = 92.360(1) degrees, and Z = 4. Broad superstructure peaks are observed in the X-ray diffraction data, indicative of a poorly ordered, doubled supercell along both the a and b axes. The quaterthiophene segment of AEQT(2+) is nearly planar, with a syn-anti-syn relationship between adjacent thiophene rings. Each quaterthiophene chromophore is ordered between nearest-neighbor lead(II) bromide sheets in a herringbone arrangement with respect to neighboring quaterthiophenes. Room temperature optical absorption spectra for thermally ablated films of the perovskites (AEQT)PbX(4) (X = Cl, Br, I) exhibit an exciton peak arising from the lead(II) halide sheets, along with absorption from the quaterthiophene moiety. No evidence of the inorganic sheet excitonic transition is observed in the photoluminescence spectra for any of the chromophore-containing perovskites. However, strong quaterthiophene photoluminescence is observed for X = Cl, with an emission peak at approximately lambda(max) = 532 nm. Similar photoluminescence is observed for the X = Br and I materials, but with substantial quenching, as the inorganic layer band gap decreases relative to the chromophore HOMO-LUMO gap.

Perovskite Materials for Light‐Emitting Diodes and Lasers

“…Although charge transport between the inorganic layers is limited due to the large spacing between the individual layers, vertical-crystal-growth (i.e., inorganic sheets perpendicular to the substrate surface) techniques could help overcome this limitation. [17,51] The increased structural freedom creates new possibilities to incorporate larger and more complex structures with tailored photophysical and electronic-transport properties beyond the archetypal perovskite structure, such as conjugated systems with π-π interactions (e.g., phenylethylamines [49] ), organic dyes (e.g., thiophenes [52] ), or fluorophores. However, the nature of the intercalated molecules has implications with respect to the layered structure.…”

“…For example, well-ordered inorganic CuX 6 octahedral layers are formed in (C 6 H 5 (CH 2 ) 2 NH 3 ) 2 CuX 4 (X = Br − or Cl − ), in which the ammonium groups are hydrogen bonded to the halides, while distorted layered structures are formed with PbCl 6 -based perovskites. [24,52] In addition, the optical performance is strongly dependent on the chain length of the R-group in R-NH 3 + . [62,63] A five-fold PL increase was observed in (C 6 H 5 (CH 2 ) m ) 2 PbBr 4 by changing m from 1 to 2.…”

Two-dimensional organic-inorganic hybrid perovskite: from material properties to device applications

“…Early in the 1970s, researchers had published papers about 2D perovskite materials in theoretical modelling [29][30][31][32][33][34] [35][36][37]. One of the two molecules must be sufficiently small to satisfy the tolerance limits, thus steadily existing in the gap of metal-halogen octahedron frame, named as small organic cation (A).…”

Mixtures of quasi-two and three dimensional hybrid organic-inorganic semiconducting perovskites for single layer LED

“…It is presumed that small variations in a, b, c are due to the inherent instabilities of the 2D layer, attributed to the NH 3 head coupling to the inorganic layer. Moreover, it is possible that synthesis or re-crystallization with DMF slightly alters the unit cell [55,56]. Finally, it is noted that the actual geometrical packing of the OL molecule in the crystal structure of the associated 2D HOIS has not been determined yet and work on this is in progress.…”