A series of donor/acceptor carbazole copolymers comprising alternating 6,7‐diphenyl‐4,9‐bis‐(thiophen‐2‐yl)‐[1,2,5]thiadiazolo[3,4‐g]quinoxaline and 3,6‐dimethyl‐9‐alkyl‐9H‐carbazole repeat units ( P1 ), or 3,6‐dimethyl‐9‐triarylamino‐9H‐carbazole repeat units ( P2 ), or 9‐triarylamino‐9H‐carbazole repeat units ( P3 ) has been prepared following Suzuki polymerization procedures. P3 absorbs light up to 1 200 nm and has an energy gap of 1.1 eV, while P1 and P2 have energy gaps of 1.3 and 1.25 eV, respectively. Photovoltaic cells with ITO/PEDOT:PSS/ P3 :PCBM (1:1 w/w)/Ca showed an open‐circuit voltage of 0.4 V under white light illumination, power conversion efficiency of 0.61%, and short‐circuit current of 5.2 mA · cm−2.
The optical properties of microcavities (MCs) are strongly dependent on both polarization of incident and emitted light and its angle of observation. Here we report the measurements of cw- and time-resolved photoluminescence (PL) observed at negative detuning and at resonance for s- and p-polarization in the strong coupling regime of a planar MC containing J-aggregates of a cyanine dye. Following non-resonant excitation, the emission spectra consist of three types of features: direct J-aggregate exciton emission, polariton emission, and uncoupled monomer emission through the transmission maxima of the distributed Bragg reflector beyond the stop-band. We compare our experimental results with a transfer-matrix calculation of the transmission for s- and p-polarization and explain the different positions of the polariton branches, the stop-band width, and the high- and low energy transmission maxima of the MC. Time-resolved PL experiments show an increase in the decay lifetime of the exciton-like mode when it is positioned far from the cavity mode. Close to resonance, the lower polariton branch decays with the natural lifetime of the J-aggregates. 相似文献
A new series of mixed oxide superconductors with the stoichiometric composition La2−xDyxCayBa2Cu4+yOz (x=0.0 − 0.5, y=2x) has been studied for structural and superconductiong properties. Our earlier studies on La2−x(Y/Er)xCayBa2Cu4+yOz series, show a strong dependence of Tc on hole concentration (psh). In the present work, the results of the analysis of the neutron diffraction measurements at room temprerature on x=0.3 and 0.5 samples are reported. It is interesting to know that Ca substitutes for both La and Ba site with concomitant
displacement of La onto Ba site. Superconductivity studies show that maximum Tc is obtained for x=0.5, y=1.0 sample (Tc ∼ 75 K), for La1.5Dy0.5Ca1Ba2Cu5Oz (La-2125). 相似文献