Abstract  A new perylene diimide derivative, namely N,N'-diallyl-1,6,7,12-tetraphenoxyperylene-3,4:9,10-tetracarboxylic acid diimide (phenoxy-allyl-PTCDI, abbreviated PA-PTCDI), is introduced. The investigations presented in this paper aim at finding a molecule for use as a sensitzer in thin film silicon solar cells in order to enhance efficiency. The synthesis is described along with optical and electrochemical measurements of PA-PTCDI in solution. A good agreement is found between the measured data and theoretical calculations. The molecule is characterized further by optical and photoemission data on thin films, which also show that the dye can be sublimed in vacuum. The interface between the dye and silicon is investigated on the model system Si(111):H with synchrotron-induced photoemission spectroscopy. The result is an electronic lineup with the gap centers of silicon and PA-PTCDI almost at identical positions and thus very similar band discontinuities from the lowest unoccupied molecular orbital (LUMO) to the conduction band as well as from the highest occupied molecular orbital (HOMO) to the valence band. This clearly permits a transfer of photogenerated electrons and holes from PA-PTCDI to silicon. The experimental valence band discontinuity matches very well the value calculated for a very similar PTCDI molecule.

Abstract  Three new derivatives of triphenylamine containing different number of 1,8-naphthalimide moieties linked via ethynyl linkages were obtained by a Sonogashira cross-coupling reaction and their properties were studied. The glass-forming derivatives showed glass transition temperatures ranging from 73 to 96 degrees C. They showed high thermal stabilities with the temperatures of the onset of thermal degradation ranging from 421 to 462 degrees C. Fluorescence quantum yields of the dilute solutions in nonpolar solvents of the compounds ranged from 0.063 to 0.94 while those of the solid films were in the range of 0.011-0.25. Small singlet-triplet gap was predicted by DFT calculations, which was confirmed by the similarity between the prompt and the delayed fluorescence energies. Cyclic voltammetry measurements revealed close values of the solid state ionization potentials ranging from 5.48 to 5.61 eV and electron affinities ranging from -3.29 to -3.16 eV. The layer of 4,4'-((di(N-(2-ethylhexyl)-1,8-naphthalimide-4-yl)phenyl)ethynyl)benzenamine exhibited effective charge-transport with hole drift mobilities exceeding 10(-2) cm(2)/Vs. Good intrinsic hole transport parameters were predicted by theoretical estimations. Both efficient fluorescence and high hole mobilities are found to be positively influenced by the presence of ethynyl bridges, (i) allowing for molecular planarization and high hole mobility and (ii) inducing large space separation between the HOMO and LUMO localizations, with direct impact in singlet triplet splitting.

Abstract  Solution-processable donor-acceptor molecules consisting of triphenylamine core and 1,8-naphthalimide arms were designed and synthesized by palladium-catalyzed Heck reaction. Dilute solutions of the synthesized compounds show strong absorption peaks in the visible wavelength range from 400 to 550 nm, which can be ascribed to the intramolecular charge transfer. Fluorescence quantum yields of dilute solutions of the synthesized materials range from 0.45 to 0.70, while those of the solid samples are in the range of 0.09-0.18. The synthesized molecules exhibit high thermal stability with the thermal degradation onset temperatures ranging from 431 to 448 degrees C. The compounds form glasses with glass-transition temperatures of 55-107 degrees C. DFT calculations show that HOMO and LUMO orbitals are almost entirely localized on the donor and acceptor moieties, respectively. Consequently, the frontier orbital energies for the three synthesized compounds are similar and practically do not depend on the number of 1,8-naphthalimide moieties. Ionization potentials of the solid samples (5.75-5.80 eV) are comparable. The charge-transporting properties of the synthesized materials were studied using xerographic time-of-flight method. Hole mobilities in the layers of the compounds having one and two 1,8-naphthalimide moieties exceed 10(-3) cm(2).V-1.s(-1) at high electric fields at room temperature. The differences on the hole mobilities between the three synthesized compounds are discussed in the frame of Marcus theory by comparing the reorganization energy and electronic coupling parameters.

Abstract  Structural properties of a single crystal and of a thin film of 3,4,9, 10-perylene-tetracarboxylic-acid-diimide are compared. The two samples are both obtained from the vapour phase, the latter being deposited at room temperature, in an ultrahigh vacuum environment, on a clean Pt(100) substrate. In the single crystal we have pointed out interactions between adjacent molecules by overlapping of the pi systems in the stacks and by hydrogen bonds between neighbouring stacks. The various surface unit cells of the nanocrystals from the film, identified by means of scanning tunnelling microscopy, are not comparable to those expected from the X-ray diffraction study of the single crystal and to those already published for other substrates. This fact clearly highlights the role played by the type of substrate chosen and/or the substrate-molecule interaction that affects the stacking and crystallinity of the growing crystal on top. (c) 2006 Elsevier B.V All rights reserved.

Abstract  The [Ru(II) (phen)(2)(pPDIp)](2+) complex, where pPDIp is the symmetric bridging ligand phenanthroline-perylene-phenanthroline, shows strong electronic absorption bands attributed to the pPDIp and {Ru(phen)(2)}(2+) moieties in acetonitrile. The charge-separated intermediate {Ru(III) (phen)(2)(pPDIp(-center dot))} was detected by transient absorption spectroscopy upon electronic excitation in either the pPDIp or the complex moieties. The charge-separated intermediate species decays to generate the triplet state (3)*pPDIp-Ru(II) (tau(P) = 1.8 mu s) that sensitizes the formation of singlet molecular oxygen with quantum yield phi(Delta) = 0.57. The dyad in deaerated acetonitrile solutions is reduced by triethylamine (NEt3) to the [Ru(II) (phen)(2)(pPDIp(center dot-))] radical anion in the dark. The electron-transfer reaction is accelerated by light absorption. By photolysis of the radical anion, a second electron transfer reaction occurs to generate the [Ru(II)(phen)(2)(pPDIp(center dot-))] dianion. The changes of the color of solution indicate the redox states of complexes and offer a sensitive reporter of each stage of redox reaction from start to finish. The reduced complexes can be converted to the initial complex, using methyl viologen or molecular oxygen as an electron acceptor. The accumulation of electrons in two well-separated steps opens promising opportunities such as in catalysis.

Abstract  A series of novel zinc complexes containing 4-2',2"-dipyridylamino-1,8-naphthalimide have been synthesized by a concise route. The luminescent properties of these materials have been investigated. Complexes Zn (N-pentyl-4-2',2"-dipyridylamino-1,8-naphthalimide)Cl-2 and compound 6 Zn(SMDP)Cl-2 show strong fluorescence in solution. In solid state the coordination of 1 and 5 ligands to a zinc center cause a blue shift of emission wavelength. They have absorption bands in the UV or near-UV region, and have the potential function as fluorescent sensors.

Abstract  The charge generation and recombination processes following photo-excitation of a low-bandgap polymer:perylene diimide photovoltaic blend are investigated by transient absorption pump-probe spectroscopy covering a dynamic range from femto-to microseconds to get insight into the efficiency-limiting photophysical processes. The several tens of picoseconds, and its efficiency is only half of that in a polymer:fullerene photoinduced electron transfer from the polymer to the perylene acceptor takes up to blend. This reduces the short-circuit current. Time-delayed collection field experiments reveal that the subsequent charge separation is strongly field-dependent, limiting the fill factor and lowering the short-circuit current in polymer:PDI devices. Upon excitation of the acceptor in the low-bandgap polymer blend, the PDI exciton undergoes charge transfer on a time scale of several tens of picoseconds. However, a significant fraction of the charges generated at the interface are quickly lost because of fast geminate recombination. This reduces the short-circuit current even further, leading to a scenario in which only around 2596 of the initial photoexcitations generate free charges that can potentially contribute to the photocurrent. In summary, the key photophysical limitations of perylene diimide as an acceptor in low-bandgap polymer blends appear at the interface between the materials, with the kinetics of both charge generation and separation inhibited as compared to that of fullerenes.

Abstract  We demonstrate new fluorophore-labelled materials based on acrylamide and on oligo(ethylene glycol) (OEG) bearing thermoresponsive polymers for sensing purposes and investigate their thermally induced solubility transitions. It is found that the emission properties of the polarity-sensitive (solvatochromic) naphthalimide derivative attached to three different thermoresponsive polymers are highly specific to the exact chemical structure of the macromolecule. While the dye emits very weakly below the LCST when incorporated into poly(N-isopropylacrylamide) (pNIPAm) or into a polyacrylate backbone bearing only short OEG side chains, it is strongly emissive in polymethacrylates with longer OEG side chains. Heating of the aqueous solutions above their cloud point provokes an abrupt increase of the fluorescence intensity of the labelled pNIPAm, whereas the emission properties of the dye are rather unaffected as OEG-based polyacrylates and methacrylates undergo phase transition. Correlated with laser light scattering studies, these findings are ascribed to the different degrees of pre-aggregation of the chains at low temperatures and to the extent of dehydration that the phase transition evokes. It is concluded that although the temperature-triggered changes in the macroscopic absorption characteristics, related to large-scale alterations of the polymer chain conformation and aggregation, are well detectable and similar for these LCST-type polymers, the micro-environment provided to the dye within each polymer network differs substantially. Considering sensing applications, this finding is of great importance since the temperature-regulated fluorescence response of the polymer depends more on the macromolecular architecture than the type of reporter fluorophore.

Abstract  A novel intramolecular donor-acceptor system of four isomers consisting of 7H-benzimidazo(2,1-a)benz(d,e)isoquinolin-7-ones and diarylamine units was synthesized and characterized: the absorption and fluorescence spectra of the system in a variety of solvents were investigated. Intramolecular charge transfer was confirmed within the system by virtue of shifts in emission maximum with increasing solvent polarity; a high dipole moment for the intramolecular excited State Was calculated using the Lippert equation. Shorter lifetimes were observed in polar solvents compared with those in non-polar solvents, indicating strong dipole-dipole interactions occurred. The ground-state geometry, lowest energy transition and the UV-vis spectrum Of the system Were Studied using density functional theory and time-dependent density functional theory at B3LYP/6-31G' level, which showed that the Calculated outcomes were in good agreement with experimental data. (C) 2008 Elsevier Ltd. All rights reserved.

Abstract  The synthesis, characterization, and photovoltaic performance of a series of N-annulated PDI materials is presented. Four novel N-annulated PDI compounds are reported, each of which can be synthesized in gram scale without the need for purification using column chromatography. N-Annulation of the PDI chromophore results in a decrease in electron affinity and lowering of the ionization potential, and renders the chromophore insoluble in organic solvents. Installation of an alkyl group improves the solubility. Single crystal X-ray analysis reveals a bowing of the aromatic backbone and compression of phenyl rings adjacent to the N atom. A brominated N-annulated PDI derivate represents a valuable synthon for creating novel multi-PDI chromophore materials. To demonstrate the utility of the new synthon for making electron transporting materials, a dimerization strategy was employed to create a dimeric PDI material. The PDI dimer has excellent solubility and film forming ability along with energetically deep HOMO and LUMO energy levels. X-ray crystal structure analysis reveals that, despite the isotropic nature of the molecule, only 1-D charge transport pathways are formed. Solar cells based on the new PDI dimer with the standard donor polymer PTB7 gave a high power conversion efficiency of 2.21% for this system. Through N-alkyl chain modification this PCE was increased to 3.13%. Further increases in PCE to 5.54% and 7.55% were achieved by using the more advanced donor polymers PTB7-Th and P3TEA, respectively. The simple yet high performance devices coupled with the highly modular and scalable "acceptor" synthesis make fullerene-free organic solar cells an attractive and cost-effective clean energy technology.

Abstract  Four electron deficient small molecules based on the diketopyrrolopyrrole (DPP) chromophore were synthesized using microwave-assisted direct arylation reactivity. These molecules are based upon an acceptor-donor-acceptor-donor-acceptor (A(1)-D-A(2)-D-A(1)) framework, where DPP is utilized as the central acceptor (A(2)) unit. We compared the effect of naphthalimide vs. phthalimide terminal acceptors (A(1)), and different DPP (A(2)) alkyl groups, on the optical, thermal, electrochemical and electronic properties. A combination of absorption and emission spectroscopy, differential scanning calorimetry, thermal gravimetric analysis, cyclic voltammetry, ultraviolet photoelectron spectroscopy, charge carrier mobility, and DFT calculations were used to characterize the four materials. All compounds were found to have narrow band-gaps, deep HOMO/LUMO levels, and were able to effectively act as electron transport materials.

Abstract  A series of novel 6-(2-substituted-1,3,4-oxadiazol-5-yl)-2-phenylthieno[2,3-d]-pyrimidine fluorescent compounds were obtained by the condensation of 6-(2-methylthio-1,3,4-oxadiazol-5-yl)-2-phenylthieno[2,3-d]pyrimidine with appropriate secondary amines. The structures were characterized by 1R, (1)H NMR, mass, elemental analysis and UV-vis spectroscopy and the fluorescence characteristics were investigated in ethyl acetate and acetone by UV-vis absorption and emission spectra. The absorption spectra and fluorescence characteristics were correlated with substituents of the 6-(2-substituted-1,3,4-oxadiazol-5-yl)-2-phenylthieno[2,3-d]pyrimidine compounds and solvent polarity. The novel compounds also displayed intense blue to yellow-green fluorescence in ethyl acetate and acetone solutions. (c) 2008 Elsevier Ltd. All rights reserved.

Abstract  Four novel naphthalimide-based dyes (D-1, D-2, D-3 and D-4) were synthesized and utilized as sensitizers in dye-sensitized solar cells (DSCs), in which the triphenylamine (TPA) or indoline groups, naphthalimide unit and carboxylic group were functionalized as electron donor, acceptor and anchoring group, respectively. The naphthalimide unit was employed as the pi-conjugation ring and electron acceptor for effectively realizing intramolecular charge separation in the oxidized states. In the series of dyes, the LUMO orbital is delocalized mainly on naphthalimide moieties, especially on the carbonyl group. Consequently, the LUMO electrons are isolated from the carboxyl anchoring group (-CH2CO2H) due to the presence of the methylene group, which could suppress the electron injection efficiency from the excited dyes to the TiO2 conduction band, thus leading to the inferior efficiencies of 1.10, 1.18, 2.27 and 2.70%, respectively, even though they exhibit broad spectral response and high extinction coefficients. (C) 2011 Elsevier Ltd. All rights reserved.

Abstract  We report the first experimental example, to our knowledge, of reversible switching between a molecular and a charge transfer phase in an organic semiconductor. An oriented film of liquid crystal perylene diimide molecules reversibly switches between a red phase with narrow conduction and valence bands and a large bandwidth black phase as the pi-stacked chromophores shift just 1.6 angstrom relative to their neighbors. This shift causes a substantial change in the intermolecular electronic overlap between molecules. The polarization of maximum absorbance rotates similar to 90 degrees, from an apparently molecule centered transition to an intermolecular charge transfer (CT) transition polarized along the pi-pi stacking axis. The experimental results are further explored via density functional theory calculations on a dimer model that demonstrate the variations in energy and oscillator strength of the molecular (Frenkel) and CT transitions as the longitudinal molecular offset is varied. These results demonstrate the exquisite sensitivity of the electrical properties of organic semiconductors to slight variations in molecular stacking.

Abstract  In the present work, we investigated the bias stress (BS) effect taking place in inkjet-printed n-type N,N'-bis(n-octyl)-1,6-dicyanoperylene-3,4:9,10-bis(dicarboximide) (PDI8-CN2) transistors fabricated on SiO2 gate dielectric. PDI8-CN2 films were deposited from solvent systems able to improve the layer structural uniformity. These devices were found to exhibit largely negative threshold voltages (V-th) and operate both as accumulation- and depletion-mode transistors. Hence, the BS phenomenon was analyzed by recording the I-DS(t) time curves when the devices were driven under both negative and positive gate-source voltages (V-GS). The BS measurements performed in this work confirm the conventional decay of the I-DS(t) when positive V-GS values (charge accumulation regime) are applied. On the other hand, I-DS(t) increases very rapidly when the devices are polarized with negative V-GS (charge depletion regime). The data achieved for the inkjet-printed devices were also compared with those measured under the same stressing conditions for a device fabricated by evaporating PDI8-CN2 on the same SiO2 substrate type. All the experimental observations reported in this work support the validity of a recently-proposed model, prompting for the occurrence of electrochemical reactions involving PDI8-CN2 molecules and ambient agents (i.e. O-2 and H2O) as origin of the BS phenomenon in these n-type field-effect transistors. (C) 2013 Elsevier B.V. All rights reserved.

Abstract  The controlled self-assembly of precise and well-defined photochemically and electrochemically active carbohydrate-coated nanoparticles offers the exciting prospect of biocompatible catalysts for energy storage/conversion and biolabeling applications. Here an aqueous nanoparticle system has been developed with a versatile outer layer for host-guest molecule encapsulation via β-cyclodextrin inclusion complexes. A β-cyclodextrin-modified polystyrene polymer was first obtained by copper nanopowder click chemistry. The glycopolymer enables self-assembly and controlled encapsulation of tetrazine-naphthalimide, as a model redox-active agent, into nanoparticles via nanoprecipitation. Cyclodextrin host-guest interactions permit encapsulation and internanoparticle cross-linking for the formation of fluorescent compound and clustered self-assemblies with chemically reversible electroactivity in aqueous solution. Light scattering experiments revealed stable particles with hydrodynamic diameters of 138 and 654 nm for nanoparticles prepared with tetrazine, of which 95% of the nanoparticles represent the smaller objects by number. Dynamic light scattering revealed differences as a function of preparation method in terms of size, 3-month stability, polydispersity, radius of gyration, and shape factor. Individual self-assemblies were visualized by atomic force microscopy and fluorescence microscopy and monitored in real-time by nanoparticle tracking analysis. UV-vis and fluorescence spectra provided insight into the optical properties and critical evidence for host-guest encapsulation as evidenced by solvachromatism and enhanced tetrazine uptake. Cyclic voltammetry was used to investigate the electrochemical properties and provided further support for encapsulation and an estimate of the tetrazine loading capacity in tandem with light scattering data.

Abstract  Two novel fluorescent brightening agents (compounds 3a-b shown in Figure 1) were synthesized, using a facile three-step synthetic route, from 4,4'-diamino-2,2'-disulfonic-stilbene, cyanuric chloride, and a readily cross-linkable 3-aminopropyltrimethoxy silane. The products contain hydrolytically active trimethoxysilyl, (-Si(OCH)(3)), functional groups that readily hydrolyze in the presence of water, and subsequently generate a water insoluble silicon cross-linked-network (Si-O-Si) via a condensation process. The cross-linked product hydrolyzes on treatment with hot aqueous sodium hydroxide to silanols (-Si(OH)(3)) to form compounds 4a-b which are readily water soluble and produce a clear fluorescent solution. The silanol forms of compounds 4a-b were used for further characterization and performance evaluation. The structures of compounds 4a-b were characterized by H-1-NMR, Fourier-Transform infrared (FT-IR) spectroscopy and negative electrospray ionization mass (-ESI-MS) spectroscopy. Compounds were applied to cotton fiber as fluorescent brightening agents and their performance was evaluated by measuring the degree of whiteness, ultraviolet protection factor (UPF), fluorescence and acid fastness. Results showed that application of 0.25% (o.w.f) of compounds 4a-b impart a high degree of whiteness (CIE WI = 144, 139) as well as good ultraviolet protection factor (UPF = 29, 27) on cotton fiber exhibiting a significant increase in whiteness and UV blocking properties compared to untreated substrate (CIE WI = 81, UPF = 5). Acid fastness tests of both compounds showed a slight change in fluorescence emission intensities as a function of pH. In acidic solutions, a shift in emission maximum occurs at pH 3 from 434 to 453 nm and from 435 to 457 nm, due to the protonation of amino and sulfonic groups of stilbene fluorophore which substantially reduces the quenching process. Published by Elsevier Ltd.

Abstract  Radical anions in the excited states can be treated as stronger reductants than those in the ground states. In this study, the intramolecular electron transfer (ET) processes from the excited perylene-3,4,9,10-tetracarboxydiimide radical anion (PDI center dot-*) were examined for the first time by applying the femtosecond laser flash photolysis to the dyads of PDI and acceptors (PDI-A). Efficient intramolecular ET from PDI center dot-* was detected upon the excitation of PDI(center dot-)p-yromellitimide (PI) and PDI center dot- naphthalenediimide (NDI) because of the sufficient driving forces. In particular, unprecedented ET processes were confirmed in a PDI-PDI dimer. Excitation of PDI center dot--PDI gave the shortest PDI center dot-* lifetime due to the fastest intramolecular ET. Surprisingly, an intramolecular disproportionation reaction generating the dianion of PDI and neutral PDI was confirmed upon the excitation of PDI center dot--PDI center dot-. These processes successfully simulated the photocarrier (polaron and bipolaron) generations in PDI-based n-type semiconducting materials for various organic molecular devices. Comparing the NDI-A and PDI-A dyad systems, the significant difference found in the intramolecular ET rate constants can be explained by the energy required to form the reduced spacer and the distances between the electron donors and acceptors.

Abstract  Enhancement of fluorescence from single molecules of perylene diimide (PDI) on tantalum pentoxide (Ta2O3) two-dimensional photonic crystal (PC) slabs with low background emission was observed using a single-molecule fluorescence spectroscopy technique. The fluorescence intensity of the single molecules on the PC was more than 3 times higher than that of the molecules without the PC. The performance of the PC slabs with a 100 x objective lens was evaluated by steady-state and time-resolved ensemble fluorescence measurements. The mechanism of the enhancement was attributed to coupling of an excitation laser and fluorescence to the PCs' modes. The present results yield new insights into a highly sensitive investigation of single molecules and regulation of fluorescence emission from them via the effect of PCs.

Abstract  Organic photodiodes are presented that utilize solution-processed perylene diimide bulk heterojunctions as the device photoactive layer. The polymer (9,9'-dioctylfluorene-co-benzothiadiazole; F8BT) is used as the electron donor and the N,N'-bis(1-ethylpropyl)-3,4,9,10-perylene tetracarboxylic diimicle (PDI) derivative is used as the electron acceptor. The thickness-dependent study of the main device parameters, namely of the external quantum efficiency (EQE), the short-circuit current (I(SC)), the open-circuit voltage (V(OC)), the fill factor (FF), and the dark current (I(D)) is presented. In as-spun F8BT:PDI devices the short-circuit EQE reaches the maximum of 17% and the Voc value is as high as 0.8 V. Device I(D) is in the nA mm(-2) regime and it correlates with the topography of the F8BT:PDI layer. For a range of annealing temperatures I(D) is monitored as the morphology of the photoactive layer changes. The changes in the morphology of the photoactive layer are monitored via atomic force microscopy. The thermally induced coalescence of the PDI domains assists the dark conductivity of the device. I(D) values as low as 80 pA mm(-2) are achieved with a corresponding EQE of 9%, when an electron-blocking layer (EB) is used in bilayer EB/F8BT:PDI devices. Electron injection from the hole-collecting electrode to the F8BT:PDI medium is hindered by the use of the EB layer. The temperature dependence of the I(D) value of the as-spun F8BT:PDI device is studied in the range of 296-216 K. In combination with the thickness and the composition dependence of to, the determined activation energy E(a) suggests a two-step mechanism of I(D) generation; a temperature-independent step of electric-field-assisted carrier injection from the device contacts to the active-layer medium and a thermally activated step of carrier transport across the device electrodes, via the PDI domains of the photoactive layer. Moreover, device I(D) is found to be sensitive to environmental factors.

Abstract  Four new monomer dyes, triazinylaminobenzanthrone derivatives, three of them containing a 2-hydroxybenzotriazole fragment, were synthesized. Two new polymerizable triazinylamino-benzotriazole stabilizers have been obtained as well. Two different synthetic routes for their synthesis have been experimented in order to find the better one. The course of the synthesis was monitored using a quantitative thin-layer chromatography (TLC). A benzanthrone dye, suitable for "one-step - in mass" coloration and stabilization of polymers, containing a tetramethylpiperidine (TMP) fragment, following a new approach, was synthesized. The compounds were characterized by TLC analysis, UV/vis, IR and H-1 NMR spectra. The ability of the derivatives to copolymerize with methylmethacrylate (MMA) was demonstrated, thus polymers with an intense color and fluorescence stable to solvents, were obtained. The quantity of the dye chemically bonded in polymer was estimated. A new approach for the synthesis of a benzanthrone dye containing a tetramethylpiperidine fragment suitable for "one-step" in mass coloration and stabilization of polymers was demonstrated. (c) 2006 Elsevier Ltd. All rights reserved.

Abstract  A new class of small molecules based on dicyanodistyrylbenzene combined with naphthalimide is developed for use as non-fullerene electron acceptors in bulk heterojunction organic solar cells. The optical, electrochemical, and film formation characteristics of the new materials are found to be suitable for preparing solution-processed devices. Solar cells prepared with poly(3-hexylthiophene) (P3HT) as a donor material exhibit a maximum power conversion efficiency of 2.71%.

Abstract  Diketopyrrolopyrrole (DPP)-based conjugated polymers have been successfully applied in high performance field-effect transistors and fullerene-based solar cells, but show limited application in non-fullerene solar cells. In this work, we use four DPP polymers as electron donor and a perylene bisimide dye as electron acceptor to construct non-fullerene solar cells. The donors and acceptor have complementary absorption spectra in visible and near-infrared region, resulting in broad photo-response from 300 nm to 1000 nm. The solar cells were found to provide relatively low power conversion efficiencies of 1.6-2.6%, which was mainly due to low photocurrent and fill factor. Further investigation reveals that the low performance is originated from the high charge recombination in photo-active layers. Our systematical studies will help better understand the non-fullerene solar cells based on DPP polymers and inspire new researches toward efficient non-fullerene solar cells with broad photoresponse. (C) 2016 Elsevier B.V. All rights reserved.

Abstract  Self-aggregation behavior in aqueous medium of four naphthalimide derivatives has exhibited substitution-dependent, unusual, aggregation induced emission enhancement (AIEE) phenomena. Absorption, emission, and time-resolved study initially indicated the formation of J-type fluorescent organic nanoaggregates (FONs). Simultaneous applications of infrared spectroscopy, theoretical studies, and dynamic light scattering (DLS) measurements explored the underlying mechanism of such substitution-selective aggregation of a chloro-naphthalimide organic molecule. Furthermore, transmission electron microscopy (TEM) visually confirmed the formation of ring like FONs with average size of 7.5-9.5 nm. Additionally, naphthalimide FONs also exhibited selective and specific cysteine amino acid sensing property. The specific behavior of NPCl aggregation toward amino acids was also employed as a molecular logic gate in information technology (IT).

Abstract  Herein, we design and synthesize a perylene diimide derivative with a fully fused backbone, FITP, which possesses an elevated lowest unoccupied molecular orbital level and high electron mobility. Consequently, polymer solar cells with FITP as the acceptor can provide the best efficiency of 7.33% with a high voltage of 0.99 V.