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For solution-based small-molecule organic photovoltaic cells (SM BHJ), thermal annealing is often regarded as a very vital processing to yield high-efficiency devices. Here, the device with the photoactive p-DTS(FBTTh2)2:PC60BM blends has been studied by varying the annealing temperature. The highest power conversion efficiency (PCE), fill factor (FF), and short-circuit current ( Jsc) has been achieved after the device was annealed at the temperature of 80 °C. X-ray diffraction (XRD) displayed that the p-DTS(FBTTh2)2 tends to form big islands with well-defined crystalline structure (long coherence length) surrounded by small islands of the PC60BM after annealing, and reached the largest grain size of 27 nm after annealing at 80 °C. AFM images demonstrated the most sufficient phase separation within the photoactive blend layer after annealing at 80 °C, which provides good photogenerated excitons dissociation. Such improvements have proved beneficial to decrease the ohmic loss and recombination in carrier-transport process via measuring series resistance and shunt resistance as well as hole mobility. This work opens up a new way to understand the relationship between thermal annealing and molecular interaction from the viewpoint of lattice relaxation. [ABSTRACT FROM AUTHOR]

Abstract: We theoretically investigate the absorption–amplification response of the probe field in a four-level cold 87Rb atomic system. It is found that the incoherent pumping fields play very important roles in realizing the amplification of the probe field. The transmission property of the probe field is also studied. [Copyright &y& Elsevier]

Abstract: All-fiber sensing system based on low-coherence interferometry, to be specific, a hybrid configuration of Mach-Zehnder and Sagnac interferometer, is widely used in long-distance distributed sensing applications. However, a lot of unwanted noises, which are difficult to be eliminated and degrade the system''s performance eventually, will be introduced between local circuits and remote sensing fiber. A novel method to reduce noise induced along transmission fiber is proposed in this paper, it utilizes two fiber Bragg gratings (FBG) with different central wavelength to generate two interferometric signals. Theoretical analysis indicates that the noises can be eliminated by the subtraction of the two signals, and simulation calculation indicates that the residual noise can be less than 1% under a typical condition. The factors which affect the proportion of residual noises are also analyzed. [Copyright &y& Elsevier]