Effective Approach toward Selective Near-Infrared Dyes: Rational Design, Synthesis, and Characterization of Thieno[3,4-]thiophene-Based Quinoidal Oligomers.

This paper describes syntheses, photophysical properties, and electrochemical characteristics of three thieno[3,4-]thiophene (TT)-based quinoidal oligomers OnTTO. The rigid planar backbones of these oligomers give the molecules narrow absorption bands, and the main absorption bands were significantly red-shifted when the TT units were extended and demonstrated wide transparent windows. The compound was found to possess strong absorption in the near-infrared (NIR) region approaching 1200 nm but remained transparent in the visible region.

Foldable semi-ladder polymers: novel aggregation behavior and high-performance solution-processed organic light-emitting transistors.

A critical issue in developing high-performance organic light-emitting transistors (OLETs) is to balance the trade-off between charge transport and light emission in a semiconducting material. Although traditional materials for organic light-emitting diodes (OLEDs) or organic field-effect transistors (OFETs) have shown modest performance in OLET devices, design strategies towards high-performance OLET materials and the crucial structure-performance relationship remain unclear. Our research effort in developing cross-conjugated weak acceptor-weak donor copolymers for luminescent properties lead us to an unintentional discovery that these copolymers form coiled foldamers with intramolecular H-aggregation, leading to their exceptional OLET properties.

Synergy between Photoluminescence and Charge Transport Achieved by Finely Tuning Polymeric Backbones for Efficient Light-Emitting Transistor.

The lack of design principle for developing high-performance polymer materials displaying strong fluorescence and high ambipolar charge mobilities limited their performance in organic light-emitting transistors (OLETs), electrically pumped organic laser, and other advanced electronic devices. A series of semiladder polymers by copolymerization of weak acceptors (TPTQ or TPTI) and weak donors (fluorene (F) or carbazole (C)) have been developed for luminescent and charge transporting properties. It was found that enhanced planarity, high crystallinity, and a delicate balance in interchain aggregation obtained in the new copolymer, TPTQ-F, contributed to high ambipolar charge mobilities and photoluminescent quantum yield.

Finely Designed P3HT-Based Fully Conjugated Graft Polymer: Optical Measurements, Morphology, and the Faraday Effect.

In this work, our group synthesized and characterized a fully conjugated graft polymer comprising of a donor-acceptor molecular backbone and regioregular poly(3-hexylthiophene) (RRP3HT) side chains. Here, our macromonomer () was synthesized via Kumada catalyst transfer polycondensation reaction based on ditin-benzodithiophene (BDT) initiator. The tin content of was then investigated by inductively coupled plasma-mass spectrometry (ICP-MS), which allowed for accurate control of donor/acceptor monomer ratio of 1:1 for the following Stille coupling polymerization toward our graft polymer ().

Design of High-Performance Organic Light-Emitting Transistors.

Organic light-emitting transistors (OLETs) integrate the light-emitting and gate-modulated electrical switching functions in a single device. Over the past decades, progress has been made in developing new fluorescent semiconductors and device engineering that pushed efficiencies of OLET devices to 8%. However, this efficiency of transistors is still too low to be competitive with organic light-emitting diodes (OLEDs).

Enhancement in Open-Circuit Voltage in Organic Solar Cells by Using Ladder-Type Nonfullerene Acceptors.

The open-circuit voltage ( V) loss has always been a major factor in lowering power conversion efficiencies (PCEs) in bulk heterojunction organic photovoltaic cells (OPVs). A method to improve the V is indispensable to achieve high PCEs. In this paper, we investigated a series of perylene diimide-based ladder-type molecules as electron acceptors in nonfullerene OPVs.

Intra-molecular Charge Transfer and Electron Delocalization in Non-fullerene Organic Solar Cells.

Two types of electron acceptors were synthesized by coupling two kinds of electron-rich cores with four equivalent perylene diimides (PDIs) at the α-position. With fully aromatic cores, TPB and TPSe have π-orbitals spread continuously over the whole aromatic conjugated backbone, unlike TPC and TPSi, which contain isolated PDI units due to the use of a tetrahedron carbon or silicon linker. Density functional theory calculations of the projected density of states showed that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) for TPB are localized in separate regions of space.

Wide bandgap OPV polymers based on pyridinonedithiophene unit with efficiency >5.

We report the properties of a new series of wide band gap photovoltaic polymers based on the -alkyl 2-pyridone dithiophene () unit. These polymers are effective bulk heterojunction solar cell materials when blended with phenyl-C-butyric acid methyl ester (PCBM). They achieve power conversion efficiencies (up to 5.