Not Accepting Doctoral Students
In a collaborative work between the departments of Chemistry, Physics, and Mathematics at UNC Chapel Hill, researchers from the Samulski Group report in the Journal of Physics D: Applied Physics on a scalable procedure for nano-patterning the bulk heterojunction layer in Organic PhotoVoltaic (OPV) devices. Nano-patterning is shown to increase light absorption.
Nano-patterning also modifies electric fields in OPV devices, thus affecting charge harvesting. The researchers present nano-patterned OPV devices with a power conversion efficiency of 4%. Comparable efficiencies are also obtained by optimization of thicknesses in a flat-layer device. Trade-offs between absorption enhancement and charge harvesting deterioration induced by nano-patterning are discussed as well as possible optimization strategies.
An international collaboration between the Samulski Group and researchers at Universita Politecnica delle Marche in Ancona, Italy, and Laboratori Llum Sincrotro in Grenoble, France, published in Physical Review Letters, shows how a bent-core mesogen that forms a cybotactic nematic phase exhibits a giant magnetic field-induced shift of its nematic-isotropic and smectic-C–nematic transition temperatures: ΔT(H)=4 K for H=10 kOe.
In contrast with molecular nematics, in cybotactic nematics the field couples with the anisotropic susceptibility of clusters containing several hundred partially ordered molecules. X-ray diffraction data corroborate a quantitative estimate of inferred cluster size (∼300 molecules). The results represent an unequivocal demonstration of the cluster picture of the nematic phase of this class of nonlinear liquid crystals.