Perylene Diimide Core Research Articles

Ortho-Heterofluorene perylenediimides: synthesis, photophysical, and exciton dynamic properties.

Previous studies suggest the perylenediimide (PDI) triplet excited state (T1) have been accessible only through bimolecular sensitization, the internal heavy-atom effect or a sophisticated cascade of nonradiative processes. Here, we designed heavy-atom-free PDIs to prompt the Tn ← S1 intersystem crossing (ISC) by introducing electron donating heterofluorene groups at the head positions of the electron-deficient PDI core. We obtained relatively high ISC efficiency up to 92% yield. Furthermore, promptly generated PDI triplets can sensitize the molecular oxygen quantitatively to yield 1O2, with singlet oxygen generation efficiencies (ΦΔ) near to unity. These results further suggest that the ISC process of PDIs can be enhanced through the intramolecular charge transfer (ICT) interaction, providing guidelines for developing triplet-generating PDIs and related rylene diimides for optoelectronic applications.

Design of perylene diimides for organic solar cell: Effect of molecular steric hindrance and extended conjugation

Core-substituted perylene diimides (PDI) are promising candidates as n-type semiconductor materials for organic photovoltaics. The chemical functionalization of perylene diimides in the bay positions is a versatile tool to obtain a series of electron acceptor materials with tunable electron affinity. These materials usually feature a donor-acceptor D-A structure in which the electron withdrawing PDI core is covalently linked with different electron donating chemical groups. The structural and electronic properties of the substituents define and modulate the optical/electrical properties of the semiconductor and the performance as photovoltaic material.In this work we designed two PDI molecules with D-A-D structure using spirobifluorene group as substituent directly linked to the perylene core (PDI-SF) and with insertion of a bithiophene moiety (PDI-BSF). In both molecules we found a reduced tendency to form aggregates in the solid state thanks to the cross-shaped rigid structure and strong steric hindrance of the spirobifluorene group. Additionally, in the case of PDI-BSF the presence of the bithiophene linker contributes significantly to extend the conjugation, resulting in a panchromatic absorption in the whole visible to NIR region. We present the synthesis of these materials and their characterisation in terms of absorption spectroscopy, cyclic voltammetry and computational calculations. Finally we show preliminary results of their use as active components in P3HT/PDIs bulk heterojunction solar cells.

Nanocoiled Assembly of Asymmetric Perylene Diimides: Formulation of Structural Factors

Nanocoiled assemblies of organic π-conjugated molecules have attracted intense attention because of their various practical applications. Herein, the assembly of highly fluorescent monolayer and bilayer nanocoils from asymmetric perylene diimide (PDI) molecules is reported. Through systematic investigation of 21 asymmetric PDI derivatives, some critical molecular structural parameters for the formation of nanocoils, involving the position of methoxy substituents at the phenyl moiety on one side and the appropriate linker that attaches the phenyl moiety to the PDI core, are formulated. The J-aggregate nature of the helical π-stacking geometry within the nanocoil is demonstrated by optical characterization. All of the nanocoils are highly emissive, with a fluorescence quantum yield greater than 25%. Furthermore, all of the nanocoils exhibited a NIR emission with a band maximum greater than 710 nm. This new class of highly NIR fluorescent nanostructures offers promising applications in areas such as optoelec...

Cooperatively Tuning Phase Size and Absorption of Near IR Photons in P3HT:Perylene Diimide Solar Cells by Bay-Modifications on the Acceptor

P3HT is a widely used and commercial polymer donor, but it cannot absorb near IR solar photons. Chemical accessibility to tune the frontier molecular orbits of π-conjugated small molecule acceptors increases the possibility to improve their near IR absorption, which is complementary to P3HT. Taking the aggregation tendency of the planar π-system into account, we herein use the traditional n-type organic semiconductor of perylene diimide (PDI) as the model backbone, showing a molecular way to cooperatively tune the aggregation tendency and absorption of the near IR photons. Practically, we replace the 2-methoxylethoxyl units from the mother PDI monomer (O-PDI-O), one-by-one, with the 4,8-bis(2-(2-ethylhexylthienyl) benzo[1,2-b′:4,5-b′]dithiophene (BDT) moieties, giving two other PDI monomers of B-PDI-O and B-PDI-B. Because of the photoinduced intramolecular charge transfer transition from the BDT unit to the PDI core, B-PDI-B exhibits a broad absorption shoulder beyond 600 nm in the dilute solution, and be...

A new class of three-dimensional, p-type, spirobifluorene-modified perylene diimide derivatives for small molecular-based bulk heterojunction organic photovoltaic devices

A new class of non-planar and three-dimensional spirobifluorene-modified perylene diimide compounds has been successfully designed and synthesized. The functionalization of the perylene diimide core with different spirobifluorene moieties can alter the molecular geometry as well as extend the spectral coverage into the red region. In addition, these compounds can be utilized as donor materials in combination with fullerene to form bulk heterojunctions, and particularly efficient organic photovoltaic (OPV) devices demonstrating high open-circuit voltages of 0.97 V and a power conversion efficiencies of up to 4% have been prepared. These values are the highest among the cells utilizing p-type perylene diimide as photoactive material in OPV devices. This work opens up a new avenue for the design and synthesis of a new class of p-type perylene diimide compounds that are promising candidates as donor materials in the fabrication of OPV devices.

Synthesis and Characterisation of 1,7‐Di‐ and Inherently Chiral 1,12‐Di‐ and 1,6,7,12‐Tetraarylperylenetetracarbox‐3,4:9,10‐diimides

AbstractBy using the Suzuki–Miyaura reaction, a variety of 1,7‐ and 1,12‐disubstituted and 1,6,7,12‐tetraaryl‐substituted perylenetetracarbox‐3,4:9,10‐diimides have been synthesised starting from the corresponding halogen derivatives. Until now, the 1,12‐ and 1,6,7,12‐sustitutions were difficult to access and only single examples have been reported. Dehydrohalogenation was observed to be competitive with the Suzuki–Miyaura reaction. The extent of this side reaction depends on the substitution pattern of the perylene diimide core and on the nature of the boronic acid derivative. Photochemical pericyclisation also reduces the yield of the desired products. A mechanistic analysis has been performed on the special case of 1,12‐diphenylperylenediimides, in which benzene is eliminated as a consecutive process of such a reaction. The energies of the frontier orbitals were determined. By using cyclic voltammetry, the energy of the LUMO was measured, and the energy gap between the frontier orbitals was determined based on optical spectroscopy (UV and fluorescence). With these two parameters, the energies of the HOMO were determined. The 1,6,7,12‐tetraaryl‐ and 1,12‐diarylperylenediimides have been optically resolved by using HPLC with a chiral stationary phase. Determination of absolute configuration was carried out by recording circular dichroism (CD) spectra of the enantiomers.

Efficient host-guest energy transfer in polycationic cyclophane-perylene diimide complexes in water.

We report the self-assembly of a series of highly charged supramolecular complexes in aqueous media composed of cyclobis(4,4'-(1,4-phenylene)bispyridine-p-phenylene)tetrakis(chloride) (ExBox) and three dicationic perylene diimides (PDIs). Efficient energy transfer (ET) is observed between the host and guests. Additionally, we show that our hexacationic complexes are capable of further complexation with neutral cucurbit[7]uril (CB[7]), producing a 3-polypseudorotaxane via the self-assembly of orthogonal recognition moieties. ExBox serves as the central ring, complexing to the PDI core, while two CB[7]s behave as supramolecular stoppers, binding to the two outer quaternary ammonium motifs. The formation of the 3-polypseudorotaxane results in far superior photophysical properties of the central PDI unit relative to the binary complexes at stoichiometric ratios. Lastly, we also demonstrate the ability of our binary complexes to act as a highly selective chemosensing ensemble for the neurotransmitter melatonin.

Small molecular non-fullerene electron acceptors for P3HT-based bulk-heterojunction solar cells

Three small molecules with the same arms and different cores of perylene diimide (PDI) or indaceno[2,1-b:6,5-b′]dithiophene (IDT) were designed and synthesized as the acceptor materials for P3HT-based bulk-heterojunction (BHJ) solar cells. The impacts of the different cores on the optical absorption, electrochemical properties, electron mobility, film morphology, photoluminescene characteristics, and solar cell performance were thoroughly studied. The three compounds possess a broad absorption covering the wavelength range of 400–700 nm and relatively low lowest unoccupied molecular orbital (LUMO) energy levels of −3.86, −3.81 and −3.99 eV. The highest power conversion efficiency of 0.82% was achieved for the BHJ solar cells based on SM3 as the acceptor material, the compound with a PDI core.

Perylene Diimide Appended with 8-Hydroxyquinoline for Ratiometric Detection of Cu2+ Ions and Metal Displacement Driven “Turn on” Cyanide Sensing

Perylene diimide (PDI) 3 and 4 appended with 8-hydroxyquinoline derivatives have been synthesized and their photophysical and spectroscopic properties have been experimentally determined. Moreover, PDIs 3 and 4 show ratiometric behavior to detect Cu(2+) colorimetrically with visible color change from coral red to light pink, whereas 3 and 4 show "turn-off" behavior in fluorescence with lowest limit of detection 5 × 10(-7) M. The PDI 3 could be further utilized for ratiometric CN(-) detection colorimetrically and as "turn-on" sensor for CN(-) detection fluorometrically with lowest limit of detection 8 × 10(-6) M. The comparison of spectroscopic properties of PDI 1-4 highlights the importance of linking 8-hydroxyquinoline units on the PDI core at bay position for achieving Cu(2+) recognition event into ratiometric signal.

Synthesis and optical properties of perylene diimide derivatives with triphenylene-based dendrons linked at the bay positions through a conjugated ethynyl linkage

A number of groups including trimethylsilyl, phenyl, triphenylene, and triphenylene-based dendron have been linked to the bay positions of a perylene diimide (PDI) core through an ethynyl bridge. The photophysical properties of the resulting bay-substituted PDI derivatives have been carefully studied in different solvents and as thin films. Without any capping group, the two ethynyl bay-substituted PDI derivates PAT and PRT both aggregate strongly even in dilute solutions but in different perylene-perylene π–π stacking modes; PRT aggregates through slipped (or longitudinal) stacking while PAT self-assembles by rotational (or cross) stacking. With capping groups, the perylene core stacking is completely blocked for PATS in both solution and solid film. For PRTS, the slipped stacking is observed only for its film sample, while for PTB, association only occurs after excitation (excimer formation). When triphenylene or triphenylene-based G1 dendron is attached to the acetylene bridge, the resulting donor–acceptor systems (PTG0 and PTG1) exhibit strong electronic coupling between the dendritic donors and the PDI acceptor, leading to significantly red-shifted absorption bands. The conjugated linkage also facilitates photoinduced electron transfer from the triphenylene or triphenylene dendron to the PDI core, effectively quenching fluorescence emissions of both the donor and the acceptor. The significantly red-shifted absorption bands and the efficient photoinduced electron transfer observed on PTG0 and PTG1 indicate that these new PDI derivatives may find applications in solar cells.

Light-controlled self-assembly and conductance: from nanoribbons to nanospheres

Photoswitchable azobenzene (AZO) chromophores were introduced to the bay-position of the traditional n-type perylene diimide (PDI). Photocontrolled self-assembly behaviours and the influence of the azobenzene substitution on the assembly structure were investigated by UV/vis spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and atomic force microscopy (AFM). Controlled morphological evolution of the nanostructures from ribbons to spheres was facilely realized by driving the azobenzene switching unit with 365 nm light irradiation. The nanoribbons demonstrated highly ordered structures while the order of the molecular arrangement was destroyed in the nanospheres, as a result of the curved molecular conformation induced by photoisomerization. In addition, the conductivity of the single nanoribbon was investigated. Thanks to the one-dimensional long-range ordered π–π stacking of the PDI cores, the nanoribbon showed good semiconducting properties with a conductance in the range of 2 × 10−5 S m−1 in air. Furthermore, the conductivity decreased with UV light irradiation, mainly due to the increased randomness within the nanostructures, representing the light-induced switching of conductance in the supramolecular systems that is extremely interesting for molecular devices.

Cross-Linked Perylene Diimide-Based n-Type Interfacial Layer for Inverted Organic Photovoltaic Devices

This contribution describes the synthesis and characterization of a perylene diimide (PDI)-based n-type semiconductor and its application to organic photovoltaic (OPV) devices having inverted architecture. Films of N,N'-bis(3-trimethoxysilylpropyl)-1,6,7,12-tetrachloroperylene-3,4,9,10-tetracarboxyldiimide (Cl(4)PSi(2)) and blends of this material with various polymers are solution-deposited on tin-doped indium oxide (ITO) substrates as interfacial layers (IFLs). The organic IFL described in this work is based on the air- and light-stable PDI core, annealed at low temperatures compatible with flexible substrates, and crosslinks in air for compatibility with device fabrication. Morphological, optical, and electrochemical analysis of these IFL films demonstrate predominantly smooth surfaces and HOMO and LUMO energies of ~4.5 and 7.0 eV, respectively, which are ideal for accepting electrons and blocking holes in inverted devices. A cationic silane species is added to the Cl(4)PSi(2) at an optimum ~2-5 wt % to reduce IFL series resistance and enhance device performance. Also, a short light soaking procedure is necessary for completed devices to achieve high fill factors in current density-voltage analysis, a phenomenon previously only observed for inverted devices having an n-type inorganic IFL.

Synthesis of Silica Encapsulated Perylenetetracarboxylic Diimide Core–Shell Nanoellipsoids

Silica encapsulated perylenediimide (PDI) nanoellipsoids with core–shell structure have been synthesized in solution by a combination of precipitation method and sol–gel chemistry. Electron energy loss spectrum (EELS) analysis proves that the obtained composite particles consist of a PDI core and a silica shell. The UV–vis and fluorescence spectra show the strong π–π stacking state of PDI molecules in the composite colloids. The silica deposition process on the PDI surface can be well controlled allowing variation of the shell thickness from 10 to 50 nm. Thermogravimetrical analysis data indicate that the thermal stability of PDI increases after deposition of a silica shell. The photostability of PDI is enhanced by the introduction of silica shell. The silica coating improves the dispersibility of PDI in different solvents and in polymer films.

Supramolecular Organization and Charge Transport Properties of Self-Assembled π−π Stacks of Perylene Diimide Dyes

Molecular dynamics (MD) simulations have been coupled to valence bond/Hartree-Fock (VB/HF) quantum-chemical calculations to evaluate the impact of diagonal and off-diagonal disorder on charge carrier mobilities in self-assembled one-dimensional stacks of a perylene diimide (PDI) derivative. The relative distance and orientation of the PDI cores probed along the MD trajectories translate into fluctuations in site energies and transfer integrals that are calculated at the VB/HF level. The charge carrier mobilities, as obtained from time-of-flight numerical simulations, span several orders of magnitude depending on the relative time scales for charge versus molecular motion. Comparison to experiment suggests that charge transport in the crystal phase is limited by the presence of static defects.

Synthesis and Optical Properties of Triphenylene-Based Dendritic Donor Perylene Diimide Acceptor Systems

A donor-acceptor charge transfer system based on two discotic mesogens has been synthesized. The donor is either a triphenylene (POG0) or a triphenylene-based conjugated dendron (POG1), while the acceptor is a perylene diimide (PDI) core. The donors are covalently linked to the bay positions of the PDI core through an ether linkage. In chloroform, due to the short donor-acceptor distance and the matching frontier orbital levels, photoinduced charge transfer from either the donor excitation or the acceptor excitation are both thermodynamically and kinetically favored, resulting in efficient quenching of both donor and acceptor fluorescence. In a less polar solvent, hexane, while charge transfer is still the dominant mechanism for decay of the excited electronic state of POG1, photoinduced charge transfer is no longer energetically favorable for POG0 when the acceptor PDI core is excited, making the PDI core of POG0 weakly fluorescent in chloroform but strongly so in hexane. In solid film, POG0 is highly aggregated through both PDI-PDI and triphenylene-triphenylene homotopic stacking. POG1, on the other hand, aggregates through triphenylene dendrons with limited PDI-PDI core stacking, presumably due to the steric hindrance caused by bulky triphenylene moieties which block the access to the PDI core. The efficient photoinduced charge transfer, coupled with the homotopic stacking that forms separated electron-transporting PDI-stacked columns and hole transporting triphenylene-stacked columns, suggests that the reported donor-acceptor systems based on dual-discotic mesogens are potentially new efficient photovoltaic materials.

Fullerodendrimers with a perylenediimide core

Dendritic C60–perylenediimide (PDI) conjugates PerG1–PerG3 have been prepared under esterification conditions starting from a perylene diol building block (Per) and fullerodendrons bearing a carboxylic acid function at the focal point. The cyclic voltammograms recorded for PerG1–PerG3 show the characteristic electrochemical features of both constitutive units, i.e.methanofullerene and PDI. The comparison with the corresponding model compounds (Per and F) shows that the oxidation of the dendrimers is centered on the PDI core, while the first reduction corresponds to a fullerene-centred process. The photophysical properties of PerG1–PerG3 and of the related reference systems Per and F were investigated in toluene solution. Per and F exhibit almost superimposed fluorescence bands sitting across the Vis and NIR spectral regions, showing that the corresponding singlet states are virtually isoenergetic (∼1.75 eV). The two bands are characterized by very different fluorescence quantum yields and short singlet lifetimes; Per: Φfluo = 7.8%, τ = 3.7 ns; F: Φfluo = 0.04%, τ = 1.8 ns. In the dendrimers, the isoenergetic singlet levels of the PDI and fullerene moieties lead to a very peculiar luminescence behaviour that is invariably found regardless of the excitation wavelength. The detected fluorescence band in PerG1–PerG3 has always the shape of the PDI central core, reduced in intensity by about 20 times compared to Per, whilst the lifetime is that of the peripheral fullerene unit. At 298 K, this unconventional behaviour is interpreted by a kinetic model involving fast equilibration of the singlet levels separated by about 0.06 eV, the PDI-centred level being the highest one. At 77 K the equilibration is suppressed and the fluorescence of the PDI central core is fully restored, showing that the corresponding level becomes lower-lying than the fullerene singlet. Bimolecular transient absorption studies made on solutions containing F and Per show that triplet energy transfer from the photoexcited fullerene to the PDI occurs. Similar investigations on PerG1–PerG3 only exhibit the features of the PDI triplet, evidencing that this level is populated in a timescale shorter than 10 ns and is the final sink of the above lying excited states. Therefore, in dendrimers PerG1–PerG3, the photophysical behaviour is not dependent on the dendrimer size and structure, and light excitation is followed by inbound energy transfer to the central core and generation of the PDI triplet state.

Synthesis of a Polymeric Electron Acceptor Based on Perylenediimide-Bridged Ladder Polysiloxane

A soluble perylenediimide (PDI) bridged ladder polysiloxane (PDI-LPS) was prepared using ladder superstructure (LS) directed dehydration polycondensation. LS was first assembled via synergistic interactions of hydrogen-bonding and π−π stacking of tetrasilanol monomers (M2s) as verified from XRD, 29Si NMR, and VPO characterizations. The ladder regularity of PDI-LPS was confirmed by a narrow half-peak width (Δ) of <1 ppm for SiO2/2 unit in the 29Si NMR spectra. The alignment of ladder chains was also demonstrated from high-resolution transmission electronic microscopy (HR-TEM) observations. We successfully used ladderlike structure to chemically confine PDI cores within one-dimensional polymeric semiconductor. The resulting PDI-LPS not only retained PDI’s optoelectronic properties but also gained enhanced solubility in common organic solvents and improved thermal stability.

Organic n-Channel Field-Effect Transistors Based on Arylenediimide-Thiophene Derivatives

The synthesis, structural, electrochemical, and thin film electrical and electronic structural properties of a series of arylene diimide-oligothiophene n-type semiconductors are reported. This family of compounds allows analysis of the effects on thin film transistor performance of the following: (i) oligothiophene backbone catenation; (ii) naphthalenediimide vs perylenediimide core interchange; (iii) phenylene group introduction in the oligothiophene backbone. Electrochemical experiments indicate similar redox energetics for all members of this series, while thin film transistor measurements reveal markedly different charge transport performances. The highest electron mobility of 0.35 cm(2) V(-1) s(-1) is recorded for films of benzo[lmn]thieno[3',4':4,5]imidazo[2,1-b][3,8]phenanthroline-1,3,6(2H)-trione, 2-octyl (NDI-1T). Solution-processed field effect transistors were also fabricated and surprisingly exhibit electrical performances surpassing that of the vapor-deposited films in the case of isoquino[6',5',4':10,5,6]anthra[2,1,9-def]thieno[3',4':4,5]imidazo[2,1-a]isoquinoline-1,3,8(2H)-trione, 2-(1-heptyloctyl)-10,12-di-2-thienyl (PDI-3T).

Photophysical study of bay substituted perylenediimides

A detailed investigation of the photophysical properties of a series of perylenediimide systems bearing three different types of bay substituents is presented. Single photon timing and femtosecond transient absorption experiments reveal that the dynamics of interconversion between two conformational arrangements of these substituents occurs with a time constant of 550 ps. In addition, charge transfer from the electron-rich units attached to the bay area of the electron-poor perylenediimide core is observed. This process leads to a fast non-radiative deactivation of the locally excited state of the perylenediimide in polar solvents. When the experimental results of the investigated systems are compared we observe a shift from a conformational dynamics towards competitive excited state processes involving charge transfer in the -meta and -para substituted perylenediimide chromophore.

Energy and charge transfer in blends of dendronized perylenes with polyfluorene

Two generations of polyphenylene dendrimers with a perylene diimide core are compared with a nondendronized tetraphenoxyperylene diimide model compound regarding their application in organic light-emitting diodes (OLEDs). Single layer devices with blends of the first and second generation dendrimers in polyfluorene are investigated as active layers in OLEDs, and the effect of dendronization on the emission color and electroluminescence intensity is studied. In photoluminescence, higher degrees of dendronization lead to a reduction in Forster transfer from the polyfluorene host to the perylene, resulting in a larger contribution of the blue host emission in the photoluminescence spectra. In electroluminescence, the dopants appear to act as active traps for electrons, resulting in a predominant generation of excitons on the dye. This gives rise to a remarkably stronger contribution of red emission in electroluminescence than in photoluminescence where energy is exchanged exclusively via Forster transfer. The pronounced color change from red to blue with higher degrees of dendronization and larger driving voltages is explained by the competition of the recombination of free electrons with holes and trapping of electrons by the emitting guest.