Pyridine−EDOT Heteroarylene−Vinylene Donor−Acceptor Polymers

Modulated charge injection in p-type dye-sensitized solar cells using fluorene-based light absorbers

In this study, new pull-push arylamine-fluorene based organic dyes zzx-op1, zzx-op2, and zzx-op3 have been designed and synthesized for p-type dye-sensitized solar cells (p-DSCs). In zzx-op1, a di(p-carboxyphenyl)amine (DCPA) was used as an electron donor, a perylenemonoimide (PMID) as an electron acceptor, and a fluorene (FLU) unit with two aliphatic hexyl chains as a π-conjugated linker. In zzx-op2 and zzx-op3, a 3,4-ethylenedioxythiophene (EDOT) and a thiophene were inserted consecutively between PMID and FLU to tune the energy levels of the frontier molecular orbitals of the dyes. The structural modification broadened the spectral coverage from an onset of 700 nm for zzx-op1 to 750 nm for zzx-op3. The electron-rich EDOT and thiophene lifted up the HOMO (highest occupied molecular orbital) levels of zzx-op2 and zzx-op3, making their potential more negative than zzx-op1. When three dyes were employed in p-type DSCs with I(-)/I3(-) as a redox couple and NiO nanoparticles as hole materials, zzx-op1 exhibited impressive energy conversion efficiency of 0.184% with the open-circuit voltage (VOC) of 112 mV and the short-circuit current density (JSC) of 4.36 mA cm(-2) under AM 1.5G condition. Density functional theory calculations, transient photovoltage decay measurements, and electrochemical impedance spectroscopic studies revealed that zzx-op1 sensitized solar cell exhibited much higher charge injection efficiency (90.3%) than zzx-op2 (53.9%) and zzx-op3 (39.0%), indicating a trade-off between spectral broadening and electron injection driving force in p-type DSCs.

Copolymerization of EDOT with pyrrole on TiO2 semiconductor films by one-step reaction, structure-dependent electronic properties, and charge conduction models of the composite films

We used the photoexcited TiO2 films to initiate the copolymerization of 3,4-ethylenedioxythiophene with pyrrole, aiming to develop an organic/inorganic heterojunction. Specular reflection infrared spectroscopy analysis was used to monitor the process of polymerization and indicated that the copolymers directly grew on the TiO2 substrate. Dissecting the copolymers with ultraviolet photoelectron spectroscopy revealed the evolution of the valence-band electronic structures. Moreover, the resulting copolymer/TiO2 heterojunctions were investigated using electrochemical impedence and X-ray photoelectron spectroscopy. The Al/poly(3,4-ethylenedioxythiophene-co-pyrrole)/TiO2/ITO heterojunction device that was prepared from the hybrid film exhibited a conspicuous rectification. The heterojunction device was also explored with respect to the conduction models.

Synthetic Aspects and Electro-Optical Properties of Fluorinated Arylenevinylenes for Luminescence and Photovoltaics

In this review, the main synthetic aspects and properties of fluorinated arylenevinylene compounds, both oligomers and polymers, are summarized and analyzed. Starting from vinyl organotin derivatives and aryl halides, the Stille cross-coupling reaction has been successfully applied as a versatile synthetic protocol to prepare a wide series of π-conjugated compounds, selectively fluorinated on the aromatic and/or vinylene units. The impact of fluoro-functionalization on properties, the solid state organization and intermolecular interactions of the synthesized compounds are discussed, also in comparison with the non-fluorinated counterparts. Luminescent and photovoltaic applications are also discussed, highlighting the role of fluorine on the performance of devices.

Synthesis of benzobisoxazole-based D-π-A-π-D organic chromophores with variable optical and electronic properties

A series of symmetrical D-π-A-π-D molecules comprised of benzo[1,2-d;4,5-d']bisoxazole (BBO) and various arylenevinylenes was synthesized via a Knoevenagel condensation of 2,6-dimethyl BBO and the corresponding aryl aldehydes. The resulting compounds had energy levels that were easily modulated and broad absorptions in the visible spectrum. They also demonstrated high fluorescence quantum yields in solution. The solvatochromism of several derivatives was examined in a number of solvents, and it was found that the emission of the triphenylamine derivative varied by almost 100 nm, depending on the polarity of the solvent. Collectively, these results indicate that the optical and electronic properties of benzobisoxazoles are readily tuned through the choice of aryl co-monomer.