Ghyung Hwa Kim

High mobility organic single crystal transistors based on soluble triisopropylsilylethynyl anthracene derivatives

A series of new anthracene based semiconductors are designed and synthesized. By substituting appropriate acenes at the 2,6-positions of triisopropylsilylethynyl anthracene (NMR, IR, DSC and TGA spectra and crystallographic information of TIPSAntBT and TIPSAntNa), two different derivatives were prepared. Especially, TIPSAntNa (naphthalene as a side group) showed superior performance when it was used as channel material. A hole mobility as high as 3.7 cm2 V−1 s−1 was obtained from single crystal OFETs. To elucidate the origin of this high performance, we carried out comparative studies to investigate the direct relationship between the molecular-packing parameters and the field-effect mobility in single-crystal OFETs because the performance of such single-crystal OFETs is not affected by defects and grain boundaries. Comparing TIPSAN single crystal OFETs having four different acene derivatives, and applying the concept of molecular overlap ratio along the long/short axis, we could show that the effective π-stacking area dominantly determines the field-effect mobility of π-stacked materials. In the case of TIPSAntNa, a large π-stacking area and a small π-stacking distance enabled the highest field-effect mobility.

Combination PBPM and Slits at the Pohang Light Source

Three combination photon beam position monitor (PBPM) and slits are in use at the photon transfer line (PTL) of the high flux macromolecular X‐ray crystallography (HFMX) beamline at the Pohang Light Source. Each slit, based on a common basic design, drives its two slit plates through a double bellows assembly by two motors. The slits also adopt a turned‐grazing inclination of 30° to restrict the passage of scattered photon beams and to enhance cooling efficiency. One of the slits has been successfully applied with cooling function in order to cool the heat load from a multi‐pole wiggler. This paper describes the design details and design features of the slits and discusses the results of performance tests for their PBPM function. The combined PBPM function can be used for the analysis of the position behaviors of photon beams at the beamline.