Jin-Liang Wang

Gradient Shape-Persistent π-Conjugated Dendrimers for Light-Harvesting: Synthesis, Photophysical Properties, and Energy Funneling

A new class of pi-conjugated dendrimers G0, G1, and G2 was developed through a double-stage divergent/convergent growth approach, in which 5,5,10,10,15,15-hexahexyltruxene was employed as the node and oligo(thienylethynylene)s (OTEs) with different lengths as the branching moieties. The dendrimers were fully characterized by (1)H and (13)C NMR, elemental analysis, gel permeation chromatography, and MALDI-TOF MS. Also, by using atomic force microscopy, it was observed that dendrimer G2 laid nearly flat on the mica surface as a single molecule. Dynamic light scattering results showed that the molecule retained its relatively flat shape in solution. To our best knowledge, dendrimer G2, with a radius approaching 10 nm and a molecular weight of 27 072 Da, was the largest among reported second generation dendrimers. The energy gradient in G2 was constructed by linking OTEs of increasing effective conjugation lengths from the dendritic rim to the core. The intramolecular energy transfer process was studied using steady-state UV-vis absorption and photoluminescent spectroscopies, as well as time-resolved fluorescence spectroscopy. Our structurally extended dendrimers showed an excellent energy funneling ability (their energy transfer efficiencies were all over 95%). All results demonstrate that these dendrimers are promising candidates as light-harvesting materials for optoelectronic devices.

Benzothiadiazole-based D-π-A-π-D organic dyes with tunable band gap: synthesis and photophysical properties.

A series of symmetrical D-π-A-π-D molecules based on benzothiadiazole and oligo(thienylenevinylene)s were facilely developed. The investigation of their photophysical and electrochemical properties demonstrated that these compounds exhibited broad absorption covering the whole visible range with appropriate energy levels for light-harvesting donors.

Solution-Processable Gradient Red-Emitting π-Conjugated Dendrimers Based on Benzothiadiazole as Core: Synthesis, Characterization, and Device Performances

A family of gradient pi-conjugated dendrimers, in which the 5,5,10,10,15,15-hexahexyltruxene unit is employed as the node, oligo(thienylethynylene)s (OTEs) are employed as light-harvesting branching units, and a 4,7-diaryl-2,1,3-benzothiadiazole is employed as the core, have been developed through the Sonogashira reaction in good yields. All dendrimers were fully characterized by (1)H and (13)C NMR, elemental analysis, and MALDI-TOF MS. Investigation of their steady-state and time-resolved photophysical properties revealed that the gradient dendritic scaffold resulted in efficient energy transfer and strong red emission. On the basis of the good solubility and excellent film forming properties, single-layer red-emitting diodes using these dendrimers as the active materials were fabricated by a simple solution spin-coating process. The moderate device performance was achieved; for example, the maximum luminance of 1290 cd/m(2) with a maximum luminescence efficiency of 1.07 cd/A was performed from BTDyn.

Star-Shaped D-π-A Conjugated Molecules: Synthesis and Broad Absorption Bands

Two donor-acceptor hybrid star-shaped D-pi-A molecules were facilely developed. The absorption spectra of TrTD2A and TrT2DA, which almost covered the whole visible range, were tuned by changing the ratio of donor and acceptor groups. However, the PL quantum efficiencies of TrTD2A and TrT2DA in solutions were dramatically reduced after the introduction of benzothiadiazole unit as acceptor chromophore.

Star-Shaped Donor-π-Acceptor Conjugated Molecules: Synthesis, Properties, and Modification of Their Absorptions Features

Well-defined star-shaped donor-pi-acceptor meta-conjugated systems with broad absorption features were constructed through facilely synthetic routes, in which triphenylamine (TPA) moiety as an electron donor and 2-dicyanomethylen-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF) unit as an electron acceptor were introduced in various ratios. The investigation of the photophysical properties indicated that the absorption bands of these compounds covered the whole visible range from 300 to 800 nm. For instance, the absorption onset of D1A2T2 was located at about 780 nm and peaked at 606 nm in thin film. The steady and transient emission spectra showed that these compounds possess an intramolecular energy transfer in such a meta-conjugation system, which was further supported by our computational investigation. Our systematic structural variation provides us insight into the tuning strategy of optical properties in D-pi-A systems and offered us a series of broad absorption molecules.

Energy Transfer in New D-π-A Conjugated Dendrimers: Their Synthesis and Photophysical Properties

A series of new D-pi-A conjugated dendrimers based on benzothiadiazole and triphenylamine were developed via facile synthetic approaches. By changing the types of bridges between the different functional moieties of these dendrimers, their photophysical properties, especially the intramolecular energy transfer process, were effectively modulated.