Fabrication of a unique white light LED from a stimuli-responsive organic molecule is reported. Emission properties are dominated by the pH of the solution through intermolecular charge transfer.

Motivated by development of lithium-ion batteries, we study the structure and dynamics of LiBF(4) in pure and mixed solvents with various salt concentrations. For this purpose, we have developed force field models for ethylene carbonate, propylene carbonate, dimethyl carbonate, and dimethoxyethane. We find that Li(+) is preferentially solvated by the cyclic and more polar component of the mixtures, as the electrostatic interaction overcomes possible steric hindrances. The cation coordination number decreases from 6 to 5 with increasing salt concentration due to formation of ion-pairs. The uniform decline of the diffusion coefficients of the two ions is disrupted at mixture compositions that perturb the ion-pair interaction. We show that the Stokes' model of diffusion can be applied to the very small Li(+) ion, provided that the size of the first solvation shell is properly taken into consideration. The strong coordination of the ions by the polar, cyclic components of the solvent mixtures established in our simulations suggests that the less polar linear component can be optimized in order to reduce electrolyte viscosity and to achieve high electrical conductivity.

Using ab initio methods we examine the molecular and solid-state electronic properties of a recently synthesized small-molecule donor, p-DTS(PTTh 2 ) 2 , which belongs to the dithienosilole-pyridylthiadiazole family of chromophores. In combination with the PC 70 BM acceptor, p-DTS(PTTh 2 ) 2 can be used to fabricate high-efficiency bulk heterojunction organic solar cells. A precise picture of molecular structure and interchromophore packing is provided via a single-crystal X-ray diffraction study; such details cannot be easily obtained with donor materials based on conjugated polymers. In first-principles approaches we are limited to a single-crystallite scale. At this scale, according to our investigation, the principal properties responsible for the high efficiency are strong low-energy light absorption by individual molecules, large exciton diffusion length, and fast disorder-resistant hole transport along π-stacks in the crystallite. The calculated exciton diffusion length is substantially larger than the average crystallite size in previously characterized device active layers, and the calculated hole mobility is 2 orders of magnitude higher than the measured device-scale mobility, meaning that the power conversion "losses" on a single-crystallite scale are minimal.