evaporation was approximately 12 cm 25 cm. The defect layer was created by the designed placement of a mask on the film during evaporation.The As 2 Se 3 coated PES film was then rolled onto the PES core and the resulting preform,~2 cm in diameter, was covered with Teflon tape and consolidated at 260 C (± 5 C) under vacuum for 20 min. The pressure was decreased quickly below 5 torr within the first 5 min. The preform was then quenched in a ±20 C freezer for about 2 min to prevent crystallization and annealed initially at 150 C and then cooled slowly for~2 h. The inner glass tube was then dissolved with HF by immersing the entire preform. After complete etching, the preform was rinsed with distilled water and isopropanol and baked under vacuum at 150 C for 5 h.Fiber Drawing: Our draw tower is composed of a three-zone vertical tube furnace (Thermcraft), a motorized capstan (Heathway) to control the speed of the drawing, and laser diameter monitors (Beta LaserMike) to monitor the outer diameter of the drawn fiber. The temperature of the upper, central, and lower zones of the oven were typically around 240 C, 295 C, and 150 C, respectively, for speeds ranging between~1±10 m s ±1 . SEM: SEM was performed on small sections of fibers embedded in epoxy resin, cut by ultramicrotome (Ultracut E, Reichert-Jung) with a diamond knife to obtain a smooth surface, and gold coated using a (Denton Vacuum) sputtercoater (~10 nm thick gold coating). We used a JEOL 6320 FEGSEM with backscattered detector at 10 keV to obtain a good contrast between the PES and As 2 Se 3 layers.Ellipsometry Measurements: The refractive indices (n,k) of As 2 Se 3 and PES were measured with a broadband spectroscopic ellipsometer (Sopra GES-5) utilizing three different detectors: photomultiplier from 250 nm to 880 nm, InGaAs from 880 nm to 2 lm, and MCT-A from 2 lm to 20 lm. Corrections were used to account for the nonlinearities and polarization dependence of the detectors. The samples consisted of a film deposited on silicon substrate. As 2 Se 3 films were deposited by thermal evaporation (similarly to the fiber fabrication process) and annealed for 1 h at 180 C, whereas PES films were spin coated (Laurell Tech. Corp. WS-400 A-6 NPP/LITE) at 1500 rpm (rpm = revolutions per minute) from a polymer solution obtained by dissolving a 25 lm PES film (Goodfellow) in N,N-Dimethylformamide. For each sample, the ellipsometric parameters tanW and cosD parameters were fitted to extract the thickness of the deposited film and to calculate n and k versus wavelength using the Levenberg±Marquardt regression method with a Cauchy-like dispersion relation and additional Lorentzian absorption peaks for PES.Fourier-Transform Infrared Spectrometer (FTIR) Measurements: Reflectivity measurements were performed using a infrared microscope (Nicolet SpectraTech NicPlan) and a FTIR (Magna 860). All backgrounds were taken using a flat gold mirror. Reflectivity spectra were normalized by a factor of~1.1 to correct assumed differences between the fiber and flat background mirror geome...

We present a setup that allows us to combinatorially study organic multilayer devices for durability and degradation mechanisms. Arrays of 8×8 thin-film organic devices are prepared by vacuum deposition and investigated under vacuum conditions. Measurements of nine types of organic solar cells are presented. Continuous solar-like illumination at 80 mW/cm2 and a temperature of 80 °C provide realistic testing conditions. The degradation of solar cells has been investigated as a function of layer combination and layer thickness over a period of 800 h. Different time scales of degradation are identified and attributed to the layer structure of the devices.

We report the synthesis, electrochemical and optical properties of novel 1,3-bis(5-diarylaminothiophen-2-yl)isothianaphthenes obtained by palladium-catalysed amination of 1,3-bis(5-bromothiophen-2-yl)isothianaphthene with diarylamines.

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We report the synthesis, characterization, and properties of a new class of hole−transport dyes, poly(dithienylisothianaphthene phenyldiamine)s (poly-DTITNPDs). These polymers are characterized by the presence of a low band gap isothianaphthene (ITN) and triarylamine units in the main chain. A modified Ullmann polycondensation reaction using a phase-transfer catalyst was utilized to prepare these polymers. The optical, thermal, and electrochemical properties were studied and compared to those of poly(triphenyldiamine ether) without having an ITN group and poly(dithienylisothianaphthene) without having triarylamine groups in the main chain. The new polymers, reported here, exhibit improved thermal stability and higher glass-transition temperatures. The incorporation of ITN group into the main chain of a polytriarylamine causes an appreciable lowering of the band gap energy up to 1.6 eV. This results in light-harvesting hole−transport dyes having less mismatch with the solar spectrum. Moreover, these polymers exhibit reversible redox behavior and possess HOMO values of about −4.7 eV and LUMO values of about −2.9 eV.