Yu Homma

Impurity doping of semiconductors is an important technique for controlling electronic and optical properties. However, it remains challenging to dope crystalline organic semiconductors, since the difference in molecular shapes and charge distribution between host and guest compounds easily degrade the crystallinity. In this study, we conducted a large-scale virtual screening of guest compounds capable of forming solid solutions with 2-decyl-7-phenyl[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-C10) host crystals. Tetracene was one of the suitable guest molecules found in this study. Tetracene-doped Ph-BTBT-C10 crystalline solid solutions were experimentally validated with the powder X-ray diffraction and photoluminescence spectra. These results demonstrate that our computational screening method is an effective approach for efficiently discovering crystalline organic semiconductor solid solutions.

Simulated absorption spectra of 1D, 2D, and 3D Phthalocyanine (Pc)-based organic semiconductor molecular thin film using Frenkel model Hamiltonian with long-range Coulomb couplings, for the study of exciton transport in optoelectronic devices.

Transient absorption spectroscopy of charge-transfer (CT) co-crystals composed of alkyl viologen dications (C _n V ²⁺ ) and a 1,3-bis(dicyanomethylene)indane anion (CMI ⁻ ) crystalline packing motifs control the formation of delocalized CT states.

Phthalocyanine (Pc)-based molecular thin films have emerged in recent years as a promising class of organic semiconductor materials for achieving a long exciton coherence length and fast exciton diffusion. However, the dependence of their exciton properties on the dimensionality and temper- ature of the Pc systems, existence of metal ions, and chemical modifications to the Pc molecule is not yet fully understood. As a first step towards a more comprehensive theoretical understand- ing of the excitonic properties of Pc thin films, we model the low-temperature exciton absorption spectra through employing the Frenkel Hamiltonian and incorporating quantum-chemistry-based site energies and exciton-exciton couplings. The predicted exciton absorption spectra of octabutoxy ph- thalocyanine (H2OBPc) was found to be strongly dependent on the dimensionality of the model as well as the distance cutoff for including the monomer-monomer exciton coupling. The best match to experimental low-temperature absorption spectra requires a 2D or 3D model and an inclusion of at least the nearest neighbor and second-nearest neighbor exciton couplings. We also caution that the widely used dipole-dipole coupling approximation could substantially overestimate the coupling of excitonic transition densities on different monomers.

A packet data transfer scheme is introduced for intra-chip data transfer to solve an interconnection problem. Double transmission lines are provided as a platform of the micronetwork. A protocol suitable for intra-chip data transfer is proposed to make the router as simple as possible. An application to a parallel VLSI processor is also discussed. In comparison with a multi-bus architecture the parallelism can be greatly increased under the same chip size because of the compactness of the micronetwork.