Enhanced absorption and fluorescence efficiency of silylethynyl-functionalized oligothiophenes and thieno[3,2-b]thiopahene

Silylethynyl-substituted oligothiophenes and thieno[3,2-b]thiophene were synthesized by the Sonogashira coupling reaction. The absorption and fluorescence maxima of these compounds shifted to longer wavelength, and they exhibited higher absorption coefficients and quantum yields than the corresponding unsubstituted molecules and tert-butylethynyl derivatives. From the DFT calculation, the energy band gap between HOMO and LUMO decreases by the introduction of a silicon atom. Thus, silyl groups can play important role in enhancing the quantum efficiency and decreasing the band-gap of chromophores. Hence, Silylethynyl group can serve as a highly efficient auxiliary for use in optical devices.     

Molecular engineering for panchromatic absorbing oligothiophene donor-π-acceptor organic semiconductors

A series of three novel organic semiconductor molecules based on the donor-π-bridge-acceptor (D-π-A) modular design have been designed, synthesised and characterised. These small organic molecules have a common donor (triphenylamine), π-bridge (an alkylated tetrathiophene) and various acceptors to provide tuning of optical and electronic properties. The examined acceptors were dicyanovinylidene, cyanopyridone and oxoindenemalononitrile groups. These compounds were highly soluble in common organic solvents, such as chloroform, toluene and chlorobenzene. As acceptor strength increased from dicyanovinylidene to cyanopyridone to oxoindenemalononitrile groups, the wavelength of the longest wavelength absorption maximum increased (518, 587, 619 nm (solution)), the respective extinction coefficients increased (4.9×10⁴, 6.3×10⁴, 7.4×10⁴ M⁻¹ cm⁻¹) and with increasing acceptor strength the band gap narrowed (1.63, 1.42 1.38 eV). Panchromatic absorbance was observed for the compounds comprising the cyanopyridone and oxoindenemalononitrile acceptors.     

氟代寡聚噻吩系列衍生物的载流子传输性质的理论研究

基于密度泛函理论方法, 采用Marcus电荷转移公式, 分别从几何和电子结构、 重组能、 转移积分及迁移率等方面研究了氟代寡聚噻吩系列衍生物中噻吩环个数、 全氟代苯位置的改变及F原子的引入对体系载流子传输性质的影响. 计算结果表明, 化合物1b, 1c和1d的电子迁移率随着噻吩单元个数的增加而逐渐升高, 因此可以通过增加噻吩单元个数来提高其电子迁移率; 而对于化合物1d, 2a和2b而言, 氟代苯位置的改变对传输性质产生了较大的影响, 其中化合物1d具有良好的平面性和π-π堆积, 传输性能最好, 有望成为良好的双极性传输材料; 比较化合物2b与3可以发现, F原子的引入增大了化合物2b的载流子迁移率, 为实验设计高迁移率的传输材料提供了理论依据.     

Harvesting solar energy using conjugated metallopolyyne donors containing electron-rich phenothiazine-oligothiophene moieties

A new family of soluble, solution-processable metallopolyynes of platinum(II) functionalized with electron-rich phenothiazine-oligothiophene rings and their corresponding dinuclear model complexes were synthesized and characterized. The organometallic polymers show different degrees of absorption capabilities in the solar spectral region, rendering some of them good electron donors for fabricating bulk heterojunction polymer solar cells by blending with a methanofullerene electron acceptor. The influence of the number of thienyl rings along the polymer chain on the optical and photovoltaic properties of these metallopolymers was studied. At the same donor:acceptor blend ratio of 1:4 or 1:5, the light-harvesting capability and solar cell efficiency notably increase as the number of thienyl rings is doubled. Photoexcitation of the polymer solar cells results in a photoinduced electron transfer from the π-conjugated metallopolyyne to [6,6]-phenyl C₆₁-butyric acid methyl ester and the best-performing polymer showed a power conversion efficiency (PCE) up to ∼1.3% with a corresponding peak external quantum efficiency of 63% under air mass (AM1.5) simulated solar illumination even at shorter absorption wavelength regime. The power dependencies of the solar cell parameters (including the short-circuit current density, open-circuit voltage, fill-factor and PCE) were also tested in detail.     

Organic photovoltaic devices with high open-circuit voltage based on oligothiophene derivatives

For the purpose of developing organic photovoltaic devices with good performance characteristics,we have fabricated twodevices using 4T-CHO,5T-CHO and PTCDA.The ITO/4T-CHO/PTCDA/Al device has a V_oc of 2.45 V and photoelectricconversion efficiency of 2.76%.The ITO/5T-CHO/PTCDA/Al device has a V_oc of 2.1 3V and photoelectric conversion efficiency of2.90%.The two devices have higher Voc(2.45 and 2.13 V).It is possible that intermolecular hydrogen bonding between-CHOgroup of nT-CHO and carboxylic dianhydride of PTCDA contribute to enhance the efficiency by promoting interfacial electrontransfer and eliminating the subconducting band trap sites.     

Thiophene‐Based,Radial π‐Conjugation: Synthesis,Structure, and Photophysical Properties of Cyclo‐1,4‐phenylene‐2′,5′‐thienylenes

The synthesis of cyclo‐1,4‐phenylene‐2′,5′‐thienylenes (CPTs) as the first example of a thiophene‐based, radially π‐conjugated system is described. X‐ray crystal structures, UV‐vis absorption and emission spectra, and theoretical studies revealed the unique structural and photophysical properties of CPTs. With all of these unique structural and photophysical properties, the radially π‐conjugated CPTs are expected to open a door for the discovery and development of new functional organic materials.     

Synthesis and luminescence properties of europium and terbium complexes with pyridine- or bipyridine-linked oligothiophene ligand

With an aim to develop novel luminescence materials, europium and terbium complexes of 2,5-(2-thiophene)-pyridine (TPY) and 5,5′-bis(5-(2,2′-bithiophene))-2,2′-bipyridine (B2TBPY) were synthesized, and their luminescence properties studied. The complexes exhibit ligand-sensitized emission, which is typical of Eu(III) and Tb(III) ions.