A photoelectronic switch of a multilevel memory device has been achieved using a meta-conjugated donor-bridge-acceptor (DBA) molecule. Such a DBA optoelectronic molecule responds to both the optical and electrical stimuli. The device exhibits good electrical bistable switching behaviors under dark, with a large ON/OFF ratio more than 10(6). In cooperation with the UV light, photoelectronic ternary states are addressable in a bistable switching system. On the basis of the CV measurement, charge carriers transport modeling, quantum chemical calculation, and absorption spectra analysis, the mechanism of the DBA memory is suggested to be attributed to the substep charge transfer transition process. The capability of tailoring photoelectrical properties is a very promising strategy to explore the multilevel storage, and it will give a new opportunity for designing multifunctional devices.

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.

Two D-pi-A conjugated molecules, BzTCA and BzTMCA, were developed through facile synthetic approaches for dye-sensitized solar cells. The investigation of the photophysical properties of BzTCA and BzTMCA both in dilute solutions and in thin films indicates that their absorption exhibits a wide coverage of the solar spectrum. The absorption features for BzTCA and BzTMCA commence at about 710 nm in solution, and at about 800 nm in the solid state. The absorption maxima (lambda(max)) for both BzTCA and BzTMCA on TiO(2) film are almost the same as those in dilute solution. Their HOMOs and LUMOs were found to partly overlap at the center of these dyes, which guarantees appreciable interactions between the donors and acceptors. The investigation of the performance of dye-sensitized solar cells fabricated from BzTCA and BzTMCA indicated that the power-conversion efficiencies are 6.04 % and 4.68 %, respectively, which could be comparable with the normal sensitizer N3. BzTMCA showed lower incident photon-to-electron conversion efficiency (IPCE) and J(sc) values relative to BzTCA, which is probably because of the weaker driving force of dye regeneration and electron injection process of BzTMCA. The IPCE responsive area reached nearly 800 nm, which provides great potential for further improvement of the photocurrent density and power-conversion efficiency. Our investigations demonstrate that both dyes BzTCA and BzTMCA could be promising candidates for dye-sensitized solar cells.

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.