Energy radiation of moving cracks

The energy radiated by moving cracks in a discrete background is analyzed. The energy flow through a given surface is expressed in terms of a generalized Poynting vector. The velocity of the crack is determined by the radiation by the crack tip. The radiation becomes more isotropic as the crack velocity approaches the instability threshold.Comment: 7 pages, embedded figure

Molecular structure-device performance relationship in polymer solar cells based on indene-C-60 bis-adduct derivatives

Interfacial tension between two materials is a key parameter in determining their miscibility and, thus, their morphological behavior in blend films. In bulk heterojunction (BHJ)-type polymer solar cells (PSCs), control of the interfacial tension between the electron donor and the electron acceptor is critically important in order to increase miscibility and achieve optimized BHJ morphology for producing efficient exciton dissociation and charge transport. Herein, we report the synthesis of a series of indene-C-60 bis-adducts (ICBA) derivatives by modifying their end-groups with fluorine (FICBA), methoxy (MICBA) and bromine (BICBA) functional units. We systematically studied the effects of their structural changes on the blend morphology with poly(3-hexylthiophene) (P3HT) and their performance in the PSCs. The end-group modification of ICBA derivatives induced a dramatic change in their interfacial tensions with P3HT (i.e., from 4.9 to 8.3mN m(-1)), resulting in large variations in the power conversion efficiency (PCE) of the PSCs, ranging from 2.9 to 5.2%