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The effect of doping carrier transporting materials being used for organic light emitting diodes was investigated in bulk-heterojunction photovoltaic devices composed of poly(3-hexylthiophene) (P3HT) and a perylene bisimide (PBI) derivative. We found that the doping of 4,4’-bis(carbazol-9-yl)biphenyl (CBP) can improve the short circuit current and fill factor with a doping concentration of 2.5wt%, resulting in an increase of power conversion efficiency from 0.14% to 0.28%. This effect is mainly attributable to the improvement of miscibility between P3HT and PBI. [ABSTRACT FROM PUBLISHER]

This work is concerned with the thermoelectromechanical fracture behavior of two coplanar cracks in a piezoelectric material strip under a uniform heat flow far away from the crack region. The crack faces are supposed to be insulated thermally and electrically. Fourier transforms are used to reduced the mixed boundary value problems to singular integral equations. Numerical calculations are carried out, and detailed results are presented to illustrate the influence of the geometric parameters on the thermal stress intensity factors. [ABSTRACT FROM AUTHOR]