Two low-bandgap (LGB) conjugated polymers ( P1 and P2) based on thiophene-phenylene-thiophene (TPT) with adequate energy levels have been designed and synthesized for application in bulk-heterojunction polymer solar cells (PSCs). The absorption spectral, electrochemical, field effect hole mobility and photovoltaic properties of LGB TPT derivatives are investigated and compared with poly(3-hexylthiophene) (P3HT). Photophysical studies reveal bandgaps of 1.76 eV for P1 and 1.70 eV for P2, which could effectively harvest broader solar spectrum. In addition, the thin film absorption coefficients of P1 and P2 are 1.6 x 10 (5) cm (-1) (lambda approximately 520 nm) and 1.4 x 10 (5) cm (-1) (lambda approximately 590 nm), respectively. Electrochemical studies indicate desirable HOMO/LUMO levels that enable a high open circuit voltage while blending them with fullerene derivatives as electron acceptors. Furthermore, both materials show sufficient hole mobility (3.4 x 10 (-3) cm (2)/Vs for P2) allowing efficient charge extraction and a good fill-factor for PSC application. High-performance power conversion efficiency (PCE) of 4.4% is obtained under simulated solar light AM 1.5 G (100 mW/cm (2)) from PSC device with an active layer containing 25 wt% P2 and 75 wt% [6,6]-phenyl-C71-butyric acid methyl ester (PC 71BM), which is superior to that of the analogous P3HT cell (3.9%) under the same experimental condition.
Four novel conjugated polymers (P1, P2, P3, and P4) based on coplanar thiophene-phenylenethiophene (TPT) derivatives have been designed and synthesized for application in polymer solar cells (PSCs). The optical, electrochemical, field effect carrier mobility, and photovoltaic properties of P1-P4 are investigated and compared with those of poly(3-hexylthiophene) (P3HT). PSCs are fabricated based on the blend of the polymers and [6,6]-phenyl-C61-butyric acid methyl ester (PC 61 BM) or 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-C-71 (PC 71 BM) with a weight ratio of 1:3. The maximum power conversion efficiency (PCE) of the PSCs based on P3/PC 71 BM system reaches 3.3% with a short circuit current density (J sc ) of 7.6 mA/cm 2 , an open circuit voltage (V oc ) of 0.8 V, and a fill factor (FF) of 0.54 under AM 1.5G (100 mW/cm 2 ) illumination. The results indicate that the coplanar TPT conjugated derivatives are promising PSC materials.
We have synthesized a series of novel coplanar chromophores in which heteroarenes, namely, thiophene, benzothiophene, and carbazole, were fused to neighboring phenylene ring(s) through intramolecular annulation via sp(3)-hybridized carbon atoms bearing two p-tolyl groups as peripheral substituents. The molecular configurations of the pi-conjugated backbones were determined by X-ray crystallographic analysis; the heteroarene-fused molecular frameworks of these novel molecules exhibit nearly coplanar conformations. [structure: see text]
BACKGROUND AND PURPOSE:Quantitative susceptibility mapping of the human brain has demonstrated strong potential in examining iron deposition, which may help in investigating possible brain pathology. This study assesses the reproducibility of quantitative susceptibility mapping across different imaging sites.
The lasers used were a XeCl laser operating at 308 nm, s pulse » 30 ns (Lambda Physik, EMG 201 MSC), and an Nd:yttrium aluminum garnet (YAG) laser, operating at the second harmonic, k = 532 nm, s pulse » 5 ns (B. M. Industries, Serie 5000).Experimental Methods: For the macroscopic mechanical actuation of the films, the laser beams were weakly focused onto the front surface of the film so that the entire surface area of the film was homogeneously irradiated (spot area: 1.5 mm 2.5 mm). A digital camera, placed at an angle of~85 to the normal to the surface, was used for monitoring the bending of the films.In the fluorescence experiments, the UV laser beam was weakly focused almost perpendicularly onto the sample in a 1.2 mm diameter spot using a quartz spherical lens (f = +500 mm). The green laser beam was also weakly focused onto exactly the same area where the UV beam is focused, almost perpendicularly to the sample. Irradiation of the samples was performed in ambient atmosphere. The fluorescence of the stable trans MC photoproducts was probed by excitation with laser pulses of 532 nm of very low fluence (F laser £ 4 mJ cm ±2 ). Photoproduct formation by the probe beam was negligible, and all recorded fluorescence can be assumed to derive exclusively from photoproducts formed by the preceding pump laser pulses. A relatively long delay (of the order of several seconds) between the pump and probe pulses was employed for ensuring that the fast-formed, metastable isomers had turned into the final/stable isomers. On the other hand, the monitoring of the metastable photoproducts was achieved by collecting the emission signals from the samples with zero delay with respect to the pump laser pulses.The induced emission was collected by an optical fiber placed nearly perpendicular to the substrate and~1±2 cm from its surface. An x±y micrometer ensured accurate positioning of the optical fiber relative to the irradiated spot. The light from the fiber was spectrally analyzed in a 20 cm grating spectrograph and recorded by a gated optical multichannel analyzer (OMA III system, EG&G PARC Model 1406). A gate time value of 1 ls was applied. Highly Efficient UV Organic Light-Emitting Devices Based on Bi(9,9-diarylfluorene)s** By Teng-Chih Chao, Yu-Ting Lin, Chen-Yu Yang, Tsung Shi Hung, Hung-Chieh Chou, Chung-Chih Wu,* and Ken-Tsung Wong*The rapid advancement of organic light-emitting devices (OLEDs) in recent years has extended the emission wavelengths over the whole visible range and has enabled realization of full-color OLED displays. Extending the emission of OLEDs into even shorter ultraviolet wavelengths, however, has not progressed as well, although compact and efficient UV emitters would find many uses in biological/fluorescent sensors, [1±2] in full-color displays by generating blue-to-red emission through pumping luminescent materials, [3] or in high-density information storage devices. [4±6] In addition, wide-gap materials are also of increasing importance in triplet emitters for electrophosphorescence. [7±9] In th...
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