Publications

Indeno[1,2-b]fluorene derivatives with trimethlysilylethynyl substituents at the 6- and 12-positions were found to undergo cyclo-dimeerzatin cyclo-trimaerzatio and higher oligomerization at room tempeatrue. The cyclic dimer feature a novel double-decker motif, composed of two face-to-face stacked bis(propadienylide)dihydroindeno[1,2-b] flourenes with a short centroid-to- centroid distance of 3.50 angstrom. The existence of a cyclic timer and higher oligemers was indeno[1,2-b]fluorene moiety.

Three triangular platinum(II) amine metallacycles incorporating large cyclic oligo(phenylene-ethynylene) (OPE) bisacetylide ligands are synthesized, and their photophysical properties are studied. Two types of triplet excited states with ligand/metal-to-ligand charge-transfer and acetylide-ligand-centered characteristics respectively, are exhibited by these complexes depending on the size (conjugation length) and electronic features of the cyclic OPE ligands. When the energy levels Of the two excited states are close to each other, the lowest triplet state is found to switch between the two in varied solvents, resulting from their relative energy inversion induced by solvent polarity change. Density functional theory and time-dependent density functional theory calculations provide corroborative evidence for such experimental conclusions. More importantly, the designed metallacycles show impressive WO-photon absorption (2PA) and two-photon excitation phosphorescing abilities, and the 2PA cross section reaches 1020 GM at 680 nm and 670 GM at 1040 nm by two different metallacycles. Additionally, pronounced reverse saturable absorptions are observed with these metallacycles by virtue of their strong transient triplet-state absorptions.

Surface reactions of 2,5-diethynyl-1,4-bis(phenylethynyl)-benzene on Ag(111), Ag(110), and Ag(100) were systematically explored and scrutinized by scanning tunneling microscopy, molecular mechanics simulations, and density functional theory calculations. On Ag(111), Glaser coupling reaction became dominant, yielding one-dimensional molecular wires formed by covalent bonds. On Ag(110) and Ag(100), however, the terminal alkynes reacted with surface metal atoms, leading to one-dimensional organometallic nanostructures. Detailed experimental and theoretical analyses revealed that such a lattice dependence of the terminal alkyne reaction at surfaces originated from the matching degree between the periodicities of the produced molecular wires and the substrate lattice structures.

Morphology control of solution coated solar cell materials presents a key challenge limiting their device performance and commercial viability. Here we present a new concept for controlling phase separation during solution printing using an all-polymer bulk heterojunction solar cell as a model system. The key aspect of our method lies in the design of fluid flow using a microstructured printing blade, on the basis of the hypothesis of flow-induced polymer crystallization. Our flow design resulted in a similar to 90% increase in the donor thin film crystallinity and reduced microphase separated donor and acceptor domain sizes. The improved morphology enhanced all metrics of solar cell device performance across various printing conditions, specifically leading to higher short-circuit current, fill factor, open circuit voltage and significantly reduced device-to-device variation. We expect our design concept to have broad applications beyond all-polymer solar cells because of its simplicity and versatility.

In this investigation, we reported the two-dimensional (2D) self-assembly of a pair of triangular macrocycles (TMC1 and TMC2) at a highly oriented pyrolytic graphite (HOPG)/1-phenyloctane interface. Although with the similar triangle-shaped phenyl backbones, TMC1 and TMC2 displayed different 2D nanopatterns. Control experiments with varying concentrations and temperatures have been carried out. Phase separations were recorded in the coassembly of TMC1 and TMC2. Scanning tunneling microscopy (STM) measurements, as well as density function theory (DFT) calculations, revealed the formation mechanism of the TMC1 and TMC2 nanoarrays. Moreover, minor ring-opening phenomena of TMC2 were detected by STM, which demonstrates the advantages of STM in trace content analysis.

3,4,9,10-Tetracyano- and tetrachlorocoronene-1,6,7,12-tetracarboxy diimides with low LUMO levels at -3.9 to -4.2 eV are developed. These molecules manifest potent n-type semiconductive capability in solution-processed field-effect transistors, with electron mobilities of up to 0.16 cm(2) V-1 s(-1) measured in air. The device performances of analogous molecules elucidate the importance of side chain structures in the semiconductive properties.

A series of triscyclometalated iridium complexes with oligofluorene-substituted ppy ligands manifest impressive two-and three-photon absorption properties. In particular, a star-shaped complex bearing three carbazole-terminated trifluorenyl ppy demonstrates a large three-photon absorption cross section up to 81 x 10(-78) cm(6) s(2) photon(-2). In combination with optimal phosphorescence quantum yields (0.5-0.8), such iridium complexes are effective two-and three-photon excited phosphorescence emitters.