High-performance organic thin-film transistor based on a dipolar organic semiconductor.

A merocyanine dye with an outstandingly large dipole moment of 14 Debye affords thin-film transistors with 0.18 cm(2) V(-1) s(-1) hole mobility and a 10(6) on/off ratio. These results suggest that molecules that lack symmetry and possess large dipole moments can perform excellent charge carrier transport contrary to established molecular semiconductor design strategies.

Parallel bulk-heterojunction solar cell by electrostatically driven phase separation.

Thermal co-evaporation of C(60) fullerene and two merocyanine dyes affords bulk heterojunction solar cells with improved short-circuit currents and power conversion efficiencies in comparison with the respective single donor cells. These results are rationalized by the formation of three distinct subphases driven by differences in molecular shape and electrostatic interactions.

Synthesis and characterization of optical and redox properties of bithiophene-functionalized diketopyrrolopyrrole chromophores.

A series of six new 2,2'-bithiophene-functionalized diketopyrrolopyrrole (DPP) dyes 7a-f bearing different electron-donating and electron-withdrawing substituents at the terminal thiophene units was synthesized by palladium-catalyzed cross-coupling reactions. The to date unknown diiodinated DPP 2 and the corresponding boronic ester derivative 3 could be prepared in high yields, and these are shown to be versatile building blocks for the synthesis of DPP-based molecular materials by Negishi, Stille, and Suzuki coupling. The influence of the peripheral substituents on the optical and electrochemical properties of the present series of DPP dyes 7a-f were investigated by UV/vis and steady-state fluorescence spectroscopy and cyclic voltammetry, revealing an appreciable effect on the electronic nature of these dyes. The diamino-substituted DPP derivative 7e exhibits a strong absorption band reaching in the near-infrared (NIR) region, which is a highly desirable feature for application in organic photovoltaics.

Near-infrared absorbing merocyanine dyes for bulk heterojunction solar cells.

A series of near-infrared absorbing merocyanine dyes bearing the strong electron-accepting 2-oxo-5-dicyanomethylene-pyrrolidine unit was synthesized and applied in combination with PC(61)BM and PC(71)BM in solution-processed photoactive layers of bulk heterojunction solar cells, exhibiting a remarkable performance range with power conversion efficiencies from 0.01% to 1.00%.

Direct comparison of highly efficient solution- and vacuum-processed organic solar cells based on merocyanine dyes.

Identically configured bulk heterojunction organic solar cells based on merocyanine dye donor and fullerene acceptor compounds (see figure) are manufactured either from solution or by vacuum deposition, to enable a direct comparison. Whereas the former approach is more suitable for screening purposes, the latter approach affords higher short-circuit current density and power conversion efficiency.