This study reports the first syntheses and characterization of 2,7-carbazolenevinylenebased oligomers and polymers. Their relatively straightforward syntheses are mainly based on Horner-Emmons or Knoevenagel coupling reaction leading to well-defined oligomers and polymers. As expected, introduction of vinylene and cyanovinylene unit into the polymer backbone decreases the band gap allowing a fine-tuning of the optical and electrical properties. These electroactive and photoactive organic materials exhibit promising performances in light-emitting devices and field-effect transistors. For instance, preliminary measurements using poly(N-(2-ethylhexyl)-2,7-carbazolenecyanovinylene-alt-2,5-dioctyloxy-1,4-phenylenevinylene) (PCCVP) have revealed orange-red emission with an intensity of 245 cd/m 2 at 10 V, whereas p-type mobility of about 3.7 × 10 -2 cm 2 /V‚s and an on/off ratio as high as 10 6 were reached with 1,4-bis(vinylene-(N-hexyl-2-carbazole))phenylene (CPC).

spectra were recorded on a Varian AS400 apparatus in appropriated deuterated solvent solution at 298 K. Chemical shifts were reported as δ values (ppm) relative to internal tetramethylsilane. Differential scanning calorimetry (DSC) was performed on Perkin-Elmer DSC7 module in conjunction with the Perkin-Elmer thermal analysis controller TAC7/DX at a heating rate of 2°C/min. UV-visible absorption spectra were recorded on a Hewlett-Packard diode-array spectrophotometer (model 8452A) using 1 cm path length quartz cells. Optical band gap was calculated from the onset of the UV-visible absorption band. For the solid state measurement, oligomer solution in THF was cast on a quartz plates. Cyclic voltammetry was carried out in a two-compartment cell with a Solartron potentiostat (model 1287) with a platinum electrodes at a scan rate of 50 mV/s against SCE reference electrode in an anhydrous and argonsaturated solution containing tetrabutylammonium perchlorate (TBAP) (10 -1 M) and oligomer (10 -4 M) in THF. Materials.All starting organic compounds were purchased from Aldrich Co. and used without further purification. All solvents used in the reactions were freshly distilled under argon. The supporting electrolyte tetrabutylammonium perchlorate was previously dried under vacuum at 60°C. Syntheses of 2,5-dimethyl-4-methoxyphenylboronic acid, 1 Pd(PPh 3 ) 4 , 2 PdCl 2 (dppf) 3 have been already reported in the literature. 2,5-dimethyl-4-(2'-nitrophenyl)anisole (1).A two-necked 500 mL flask fitted with condenser, magnetic stirring bar was charged with 15.33 g (88 mmol) of 2,5-dimethyl-4methoxyphenylboronic acid, 16.18 g (80 mmol) of 1-bromo-2-nitrobenzene, 120 mL of toluene and 80 ml of K 2 CO 3 2M. The resulting solution was degassed with a vigorous flow of argon for 30 min, then 0.92 g (1 mol%, 0.8 mmol) of Pd(PPh 3 ) 4 was added under argon and the mixture was refluxed

research is focussing on further improvements to this effi ciency, equally important fundamental research on the photophysics, photochemistry, and structure/function relationships of organic photovoltaics devices and their constituent materials remains an integral facet of this research area. Such research is vital for investigating all the steps comprising the operation of organic solar cells, from exciton generation, diffusion and dissociation to charge separation, transport and extraction.Optical and opto-electrical methodologies have been successfully applied in order to understand this organic solar cell behavior. Most common are charge carrier mobility studies, [ 4 ] using techniques such as time-of-fl ight, [5][6][7][8] photo-CELIV (photoinduced charge extraction by linearly increasing voltage), [ 5,9,10 ] space-charge limited current [ 11 ] and dark injection. [ 12 ] Other techniques such as electrochemical impedance spectroscopy (EIS), charge extraction and transient photovoltage provide information on charge carrier density, lifetime, and kinetics.In order to produce an organic photovoltaic device with a high power conversion effi ciency, the three relevant parameters to be optimized are the open circuit voltage, V OC , the fi ll factor, FF , and the short circuit current, J SC . The latter parameter, the J SC , is in turn dependent upon the effi ciencies of light absorption, charge carrier generation, and charge carrier collection ( η COLL ). A poor charge carrier collection invariably lowers the J SC and thus the overall device efficiency. The effi ciency of charge carrier collection depends on the distance charges can travel before they recombine. Under short circuit conditions, if the photocurrent response is dominated by drift, effi cient charge carrier collection requires a long charge carrier drift length, L DR . Conversely, if diffusion dominates, then effi cient charge carrier collection relies upon a long charge carrier diffusion length, L . Ideally, L should be at least three times longer than the active layer thickness, d , such that:under the condition of αd << 1, where αd is the optical density. [ 13 ] In either case, one of the most pertinent parameters It is important to accurately measure the charge carrier lifetime, a crucial parameter that infl uences the collection effi ciency in organic solar cells. Five transient and small perturbation experimental techniques that measure charge carrier lifetime are applied to a device composed of the polymer PDTSiTTz blended with the fullerene PCBM: time-resolved charge extraction (TRCE), transient absorption spectroscopy (TAS), photoinduced charge extraction by linearly increasing voltage (photo-CELIV), transient photovoltage, and electrochemical impedance spectroscopy. The motivation is to perform a comprehensive comparison of several different lifetime measurement techniques on the same device in order to assess their relative accuracy, applicability to operational devices, and utility in data analysis. The techniques all produce similar charge...