Manas Shah

Chain bridging in a model of semicrystalline multiblock copolymers.

Recent experimental observations have suggested an intimate connection between the chain conformations and mechanical properties of semicrystalline multiblock copolymers. Motivated by these studies, we present a theoretical study evaluating the bridging/looping fractions in a model of semicrystalline multiblock copolymers. We model the noncrystalline block (A) as a flexible Gaussian chain and the crystalline block (B) as a semiflexible chain with a temperature dependent rigidity and interactions that favor the formation of parallel oriented bonds. Using self-consistent field theory, the bridging fractions of the various domains in different multiblock copolymers (ABA, BAB, ABABA, and BABAB) are evaluated and compared with their flexible counterparts. In general, we observe that for both triblock and pentablock copolymers, rendering one of the blocks crystallizable promotes bridging in that component while reducing the bridging in the other noncrystallizable component. Moreover, the bridging fractions in tri- and pentablock copolymers were seen to be quantitatively similar except insofar as being normalized by the volume fraction of bridgeable units.

Effect of anisotropic charge transport on device characteristics of polymer solar cells

We present a model for photovoltaic device characteristics based on drift-diffusion ideas which allows for prescription of arbitrary morphologies of donor and acceptor phases while simultaneously incorporating the role of anisotropic charge transport of holes and excitons. We use such a model to address the interplay between anisotropic charge transport and the orientational and/or crystalline ordering of donor molecules. We presents results illustrating the influence of the degree of orientational ordering, the impact of ordering parallel and perpendicular to the electrodes and the role of device thickness.