In this work, conditions of Suzuki condensation and polymer modification of polymers of benzene and fluorene units have been studied. A new polymer was prepared with statistical equimolecular amounts of two 2,7-dibromo-9,9-bis(6′-susbtituted-hexyl)fluorene as starting monomers. The C9 position of the poly[9,9-bis(6′-bromohexylfluoren-2,7-diyl)-alt-co-(benzen-1,4-diyl has been substituted yielding poly-[9,9-bis(6′-cyanohexylfluoren-2,7-diyl)-alt-co-(benzen-1,4-diyl)] with a high degree of conversion. All polymers were completely soluble in THF and chloroform and were characterized by NMR, FTIR, and elemental analysis. Molecular weights measured by gel permeation chromatography coupled with light scattering detector results in polydispersity values between 3.3 and 1.2. Their glass transitions temperature were over 90 and 99 °C by DSC. Comparative studies of optical properties in solution and solid state show similar values indicating that the remote substitution of functional group maintains the spectroscopic characteristics of the backbone. Cyclic voltammetry studies and preliminary results in bias potentials of electroluminiscent devices reveal that these polymers may be promising candidates to be used as hole and electron transporting materials.

A visible light communication (VLC) system using an organic bulk heterojunction photodetector (OPD) is presented. The system has been successfully proven indoors with an audio signal. The emitter consists of three commercial high-power white LEDs connected in parallel. The receiver is based on an organic photodetector having as active layer a blend of poly(3-hexylthiophene) (P3HT) and phenyl C61-butyric acid methyl ester (PCBM). The OPD is opto-electrically characterized, showing a responsivity of 0.18 A/W and a modulation response of 790 kHz at −6 V.

UPCommonsPortal del coneixement obert de la UPC http://upcommons.upc.edu/e-prints Abstract: We studied the performance over time of opaque and semi-transparent PTB7:PC71BM bulk hetero-junction solar cells. For unsealed inverted configuration cells we observe that when the isolation from the environment is improved, the degradation observed is dominated by one single exponential decay. We demonstrate that a dielectric multilayer stack of approximately 550 nm provides an isolation that increases the lifetime of the cell close to ten times. In that event the fill factor appears to be the PV parameter dominating cell degradation resulting from a decrease in the shunt resistance. An Impedance analysis we performed indicates that a Warburg element, attributed to the presence of slowly moving charges such as heavy ions, must be included in thedescription of the experimental data. The contribution from such element increases as the cell degrades in good agreement with a degradation dominated by the corrosive effects from external agents reaching the active layer of the device. We have revised our manuscript according to the comments and suggestions from both reviewers. Enclosed with the manuscript we provide a detailed response to the reviewers points. Essentially, we do not have any strong disagreement with the reviewers remarks and we used their comments and suggestions to improve the manuscript. In response to the request of an ISOS-L-1 test made by reviewer#3, we provide a supplementary data file which is cited in the revised main text. With the submission we provide a detailed response to the reviewers points and an indication of the changes introduced. Additionally, we provide a copy of the text where all changes introduced are in blue.We would like to use this opportunity to thank you again for all the time and consideration dedicated to our manuscript. In the first paragraph in page 6 of the revised manuscript the following sentenceis included: For V< 0,6 V the Warburg feature is not observed and therefore R w is set to 0. The second paragraph in page 6 has been rewritten as follows: Nyquist plots at four different voltages are shown in figures 6 as examples of impedance measurements for three different times. We observe a good agreement between the experimental data and the theoretical fit. The main feature in the complex plane is a typical depressed semicircle in the medium-high frequency range, a standard behaviour in organic solar cells associated to carrier recombination. The semicircle diameter increases with time, which implies an increase of the parallel resistance R P . This leads to a corresponding rise of the recombination time and therefore to an enhancement of the carrier density. Besides, the semicircle depression is more pronounced with time, leading to a decrease of CPE P parameter, and thus moving away from the ideal capacitor behaviour. At low frequencies, for V = 0.6 and 0.8 V, one may observe a tail associated to a Warburg behaviour that is more pronounced as time evolves. This results in an ...

No abstract