Solid-state Optical Properties Research Articles

Effects of structure-manipulated molecular stacking on solid-state optical properties and device performances

Four conjugated copolymers with phthalimide (PhI) or thieno[3,4-c]pyrrole-4,6-dione (TPD) as the acceptor, thiophene (T) or selenophene (Se) as the spacer and 3,3′-didodecyl-2,2′-bithiophene (BT) as the common donor, namely, PPhI-T, PPhI-Se, PTPD-T and PTPD-Se, have been synthesized and the effects of intra- and intermolecular interactions on the optical properties, molecular stacking, and organic electronic device performances were investigated. The intramolecular S(Se)⋯O (carbonyl) interactions between the spacer and the PhI's or TPD's carbonyl and the intermolecular reciprocity between the polymeric backbones differ from each other as the spacer and the acceptor were varied. Among the four polymers, PPhI-T with the weakest intramolecular S⋯O interaction and intermolecular backbone reciprocity exhibited the poorest photovoltaic performance with a PCE of 0.31%. When the T spacer was replaced by the more polarized Se spacer, the resultant copolymer PPhI-Se exhibited stronger intra- and intermolecular interactions, resulting in better optical properties with a PCE of 0.94% when blended with PC71BM. When PhI is replaced with the more polarized TPD unit, the TPD-based polymers, PTPD-T and PTPD-Se, showed even better coplanarity compared to that of the PhI-based polymers, with a PCE of 2.04% for PTPD-T and 1.52% for PTPD-Se blended with PC71BM. To the best of our knowledge, this is the first systematic study on the influences of structure-manipulated molecular stacking on solid-state optical properties and electronic device performance through modulations of the intramolecular and intermolecular interactions.

Ab initio investigations on the crystal structure, formation enthalpy, electronic structure, chemical bonding, and optical properties of experimentally synthesized isoreticular metal–organic framework-10 and its analogues: M-IRMOF-10 (M = Zn, Cd, Be, Mg, Ca, Sr and Ba)

The equilibrium solid-state structure, electronic structure, formation enthalpy, chemical bonding, and optical properties of IRMOF-10 and its alkaline earth metal analogues M-IRMOF-10 (M = Cd, Be, Mg, Ca, Sr, Ba) have been investigated with density functional calculations. The unit cell volume and atomic positions were fully optimized with the GGA functional. This supplements the incomplete experimental structural parameters available for Zn-IRMOF-10. The calculated bulk moduli decrease monotonically from Zn to Cd, and from Be to Ba, and indicate that Zn-IRMOF-10 and its analogues are relatively soft materials. The estimated bandgap values are in the range 2.9 to 3.0 eV, indicating nonmetallic character. Importantly, the bandgaps within the M-IRMOF-10 series (containing a rather long 4,4′-biphenyldicarboxylate linker) are smaller than those within the M-IRMOF-1 series (shorter benzene dicarboxylate linker). The optical properties (dielectric function ε(ω), refractive index n(ω), absorption coefficient α(ω), optical conductivity σ(ω), reflectivity R(ω), and electron energy-loss spectrum L(ω)) of the M-IRMOF-10 series were computed. The observation of very small reflectivities over a wide energy range suggests possible uses in hybrid solar cell applications. The main characteristics of the optical properties are similar for the whole series although differences are seen in the details. An analysis of chemical bonding in the M-IRMOF-10 series reveals as might be anticipated that M–O bonds are largely ionic whereas C–O, C–H and C–C exhibit mainly covalent interactions. The BOP values of M–O decrease through the series when going from Zn to Cd, and from Be to Ba, i.e. the ionicity increases and the covalency decreases for the M–O bonds.

Trans-keto* form detection in non photochromic N-salicylidene aminomethylpyridines

Five N-(5-chloro)salicylidene aminomethylpyridine derivatives were successfully synthesized and their structural and solid state optical properties analyzed. Yellow crystalline powders of CH22L33 and CH2222L3–43–43–43–4Cl present both thermo- and photochromism whereas CH22L22 and CH222L444 do not show any switching properties, as probed by diffuse reflectance spectroscopy. Contrary to structural–optical expectations, the non-photochromic CH22L22 molecule (P21/n) shows an open crystal structure, and photochromic molecules CH2222L3–43–43–43–4Cl (P21/c) present a closed crystal packing, revealed by single crystal X-ray diffraction, which is typical of exclusively thermochromic molecules. After UV irradiation, trans-keto* emission observation in CH22L22 and CH222L444 indicates the unexpected formation of the trans-keto form in these non-photochromic anil molecules. Radiative relaxation of the trans-keto* form is in addition detected, for the first time, by fluorimetry for all N-salicylidene molecules of the series, whatever their switchable chromic properties.

Dependence of solid-state optical properties on binding groups in biphenyl acid/amine supramolecular organic complexes

Chiral carboxylic acid/amine and sulfonic acid/amine supramolecular organic complexes composed of biphenyl units were successfully prepared using achiral biphenylcarboxylic acid (or biphenylsulfonic acid) derivatives and chiral 1-phenylethylamine as component molecules. The solid-state circular dichroism (CD) and fluorescent properties of the supramolecular complexes change significantly with the type and number of binding groups.

Nonclassical Tunability of Solid‐State CD and CPL Properties of a Chiral 2‐Naphthalenecarboxylic Acid/Amine Supramolecular Organic Fluorophore

The solid-state chiral optical properties (circular dichroism and circularly polarized luminescence) of a 2-naphthalenecarboxylic acid/amine supramolecular organic fluorophore can be controlled by changing the aryl unit of the chiral 1-arylethylamine component of the molecule rather than altering the chirality of the 1-arylethylamine itself.

Interplay between solid-state organization and optical properties of thin films of poly-arylene-vinylene and -difluorinated vinylene: Fullerene blends

Nowadays considerable efforts are devoted to the synthesis of low bandgap conjugated polymers for application in organic polymer solar cells. A large variety of low bandgap polymers are prepared by alternating copolymerization of electron-donating donor and electron-withdrawing acceptor units. The interaction between these two units can reduce the polymer bandgap, increasing the sunlight absorption. Benzothiadiazole is commonly used as acceptor block unit in low bandgap polymers. In this contribution we investigate the supramolecular organization and optical properties of thin films of conjugated polymers consisting of benzothiadiazole and thiophene with electron-withdrawing difluorovinylene, and electron-donating vinylene substituents. Atomic force microscopy and spectroscopic ellipsometry are exploited for the analysis of the morphology and optical transitions, respectively. It is found that F-atoms in the vinylene unit yield a blue-shift of the absorption peaks of 0.2eV respect to the hydrogenated polymer and an increase in the absorption coefficient of fluorinated polymers, which indicates their potential application as photovoltaic material. The morphology evolution of the conjugated polymers blended with a fullerene derivate ([6,6]-phenyl C61-butyric acid methyl ester, PCBM) is also investigated by atomic force microscopy.

Low-temperature solid-state synthesis and optical properties of CdS–ZnS and ZnS–CdS alloy nanoparticles

A simple low-temperature solid-state synthetic method was employed to obtain ZnS–CdS and CdS–ZnS alloy nanoparticles. The effects of reaction sequence, reactant molar ratios, and synthesis temperature on the products were investigated. The crystal structure and morphology of the products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and fourier transform infrared (FT-IR) spectroscopy. The results show that the products are alloy nanoparticles with a cubic phase structure. The formation mechanism of the alloy nanoparticles is briefly discussed. Sufficient grinding and crystalline water may be essential to form alloy nanoparticles. Ultraviolet–visible (UV–vis) spectra show that the edge absorptions of the CdS–ZnS and ZnS–CdS nanoparticles were located between those of ZnS and CdS bulks, and the absorbance at the peak maximum was practically dependent on reaction temperature, reaction sequence, and molar ratio. Extrinsic deep-level emission resulted in strong peaks in the photoluminescence (PL) spectra. The position and intensity of the emission peaks varied with the conditions during synthesis.

Solid-state chiral optical properties of axially chiral binaphthyl acid derivatives

It is important to first determine the solid-state chiral optical properties of basic fluorescence supramolecular building blocks that can form a network structure via intermolecular interactions. Although the circularly polarized luminescence (CPL) properties of ( R)-1,1′-binaphthyl-2,2′-dicarboxylic acid with axial chirality could not be measured in either the solution or solid states, those of ( R)-1,1′-binaphthyl-2,2′-diyl hydrogen phosphate with axial chirality were successfully measured in both states. The solid-state CPL originates from the intramolecular interaction of single molecule, rather than intermolecular interactions in the crystal.

Role of Molecular Packing in Determining Solid-State Optical Properties of π-Conjugated Materials.

The optical properties of π-conjugated organic molecules in their solid state are critically important in determining performance efficiencies of optoelectronic devices such as organic light-emitting diodes and organic thin-film transistors. This Perspective discusses some recent systematic explorations aimed toward arriving at an understanding of the role that molecular packing plays in determining these properties.

Control of the Solid‐State Chiral Optical Properties of a Supramolecular Organic Fluorophore Containing 4‐(2‐Arylethynyl)‐Benzoic Acid

The solid-state chiral optical properties of a 4-(2-arylethynyl)-benzoic acid/amine supramolecular organic fluorophore can be controlled by changing the arylethynyl group of the achiral 4-(2-arylethynyl)-benzoic acid component molecule rather than the chirality of the amine component molecule.

Solid-state structure and optical properties of highly fluorescent diketopyrrolopyrrole derivatives synthesized by cross-coupling reaction

Diketopyrrolopyrrole (DPP) derivatives with four different substituents were synthesized by cross-coupling reactions. The DPP derivatives were investigated in terms of their solid-state structure, absorption, emission, and electrochemistry. The electron-donating property of each substituent causes a redshift of UV/vis absorption and emission in the solution state. Although all of the DPP derivatives have high quantum yields in solution, only butoxyphenyl-substituted DPP exhibits strong emission in the solid state.

Control of solid-state chiral optical properties of a chiral supramolecular organic fluorophore consisting of 1-pyrenesulfonic acid and chiral amine molecules

The solid-state chiral optical properties of a 1-pyrenesulfonic acid/amine supramolecular organic fluorophore could be controlled by changing the type of the aromatic ring and not the chirality of the chiral amine component molecule in the solid state.

Effect of Steric Complementarity on Solid-State Optical Properties of Ternary CT Complexes: 4,4′-Biphenyldisulfonic Acid, Aliphatic Amines, and Tetracyanoquinodimethane

Crystalline ternary charge transfer (CT) complexes were constructed for tuning colors by a supramolecular approach. The complexes are composed of 4,4′-biphenyldisulfonic acid (BPDS, donor), tetracyanoquinodimethane (TCNQ, acceptor), and aliphatic amines. Four salts of BPDS with methyl-, ethyl-, isopropyl-, or t-butylamine underwent insertion of TCNQ between biphenyl moieties to yield the CT complexes with different colors in a range of deep red to light orange. Such a color change was interpreted on the basis of crystal structures of the complexes. BPDS salts produce layer structures which provide nanospaces for TCNQ and alkyl groups. Steric complementarity in the nanospaces explains the above-mentioned color change.

Solid-state optical properties of CT complexes with ammonium anthracene-2,6-disulfonate and TCNB

Solid-state optical properties of CT complexes with ammonium anthracene-2,6-disulfonate and TCNB

1,4,7,10位に様々なアルキル基を有するテトラセンの合成と固体の光物性

1,4,7,10位に様々なアルキル基を有するテトラセンの合成と固体の光物性

The First Homochiral Diamond‐Like Coordination Polymer Containing Cubane Cluster (Cu4I4) as Connecting Node and Cinchonine as Donor‐Acceptor (or Push‐Pull Electronic Effect) Building Block

AbstractThe reaction of CuI with cinchonine (an organic donor‐acceptor chromophore) afforded a homochiral 3D diamondoid network [Cu4I4(cinchonine)2]n (1) containing a cubane cluster (Cu4I4) as a connecting node. This is the first homochiral coordination polymer with diamondoid nets containing a cluster as a connecting note. Its thermal stability and solid state optical properties such as fluorescence, circular dichroism and second‐harmonic generation response were also reported.

Solid-state optical properties of a chiral supramolecular fluorophore consisting of chiral (1 R,2 R)-1,2-diphenylethylenediamine and fluorescent carboxylic acid derivatives

By using (1 R,2 R)-1,2-diphenylethylenediamine as a chiral molecule and 2-anthracenecarboxylic acid as a fluorescent molecule, we created a chiral supramolecular organic fluorophore having circularly polarized luminescence properties in the solid-state.

Solid-state assemblies and optical properties of conjugated oligomers combining fluorene and thiophene units

Two conjugated oligomers, representing elementary segments of fluorene–thiophene copolymers, are compared in terms of the microscopic morphology and the optical properties of thin deposits. The atomic force microscopy morphological data and the solid-state absorption and emission spectra are interpreted in terms of the assembly of the conjugated molecules. The compound with a terthiophene central unit and fluorene end-groups shows well-defined monolayer-by-monolayer assembly into micrometer-long stripe-like structures, with a crystalline herringbone-type organization within the monolayers. Polarized confocal microscopy indicates a strong orientation of the crystalline domains within the stripes. In contrast, the compound with a terfluorene central unit and thiophene end groups forms no textured aggregates and the optical spectra in the solid-state are very similar to those recorded in solution, suggesting that the molecules interact only weakly in the solid. The difference in behaviour between the two compounds most probably originates from their different capability to form densely-packed assemblies of interacting π-systems.

Perfect polar stacking of parallel beloamphiphile layers. Synthesis, structure and solid-state optical properties of the unsymmetrical acetophenone azine DCA

Extraordinary high degrees of polar order can be achieved by a rational design that involves the polar stacking of parallel beloamphiphile monolayers (PBAM). This strategy is exemplified by the acetophenone azines MCA (4-methoxy-4'-chloroacetophenone azine) and DCA (4-decoxy-4'-chloroacetophenone azine). The beloamphiphile design aims to achieve strong lateral interactions by way of arene-arene, azine-azine, arene-azine and halogen-bonding interactions. Dipole-induced interactions and halogen bonding dominate interlayer interactions and halogen bonding is shown to effect the layer stacking. Crystals of DCA contain PBAMs with perfect polar order and perfect polar layer stacking, while crystals of MCA features perfect polar order only in one of two layers and layer stacking is polar but not entirely perfect. We report the synthesis of the beloamphiphile DCA, its crystal structure, and we present a comparative discussion of the structures and intermolecular interactions of MCA and DCA. Absorbance and photoluminescence measurements have been carried out for solutions of DCA and for DCA crystals. DCA exhibits a broad emission centered at 2.5 eV when excited with UV radiation. The nonlinear optical response was studied by measuring second harmonic generation (SHG). Strong SHG signals have been observed due to the polar alignment and the DCA crystal's NLO response is 34 times larger than that of urea. Optimization of the beloamphiphile and systematic SAR studies of the polar organic crystals, which are now possible for the very first time, will further improve the performance of this new class of functional organic materials. The materials are organic semiconductors and show promise as blue emitters, as nonlinear optical materials and as OLED materials.

Theoretical Calculations of the Electronic Absorption Spectra of Oxotitanium(IV) Phthalocyanine in the Solid State

Oxotitanium(IV) phthalocyanine (OTiPc) has been reported to be a near-IR-active photoconductor, where crystal modifications termed phases I, II, and Y exist. In this paper, solid-state electronic absorption spectra of OTiPc have been theoretically calculated by considering three origins (i.e., exciton, charge transfer (CT), and molecular distortion) to clarify the crystal form dependence on the large red shift of the Q absorption band and high photoconductivity of the photoactive phase II in particular. In these calculations, intermolecular interactions are included in the form of configuration interactions between exciton and CT configurations, and matrix elements were calculated using the ZINDO/S Hamiltonian in order to calculate 3D metallocomplexes. By considering 243 neighboring OTiPc molecules, our theoretical calculations have succeeded in reproducing the experimental trends of the solid-state optical properties, such as the large red shift of the Q absorption band, dependence on the incident light direction, phase dependence, and CT character, indicating the reliability of our calculations. In addition, it is demonstrated that the photoconductive properties correlate well with intermolecular resonance integrals. Calculations shown here are useful not only for understanding the solid-state electronic structures of OTiPc but also for designing new functional molecular crystals.