Dramatic inversion of charge polarity in diketopyrrolopyrrole-based organic field-effect transistors via a simple nitrile group substitution.

A record-breaking high electron mobility of 7.0 cm(2) V(-1) s(-1) for n-channel polymer OFETs is reported. By the incorporation of only one nitrile group as an electron-withdrawing function in the vinyl linkage of the DPP-based copolymer, a dramatic inversion of majority charge-carriers from holes to electrons is achieved.

Efficient diketopyrrolopyrrole-based small-molecule bulk-heterojunction solar cells with different electron-donating end-groups.

A series of small molecules that contained identical π-spacers (ethyne), a central diketopyrrolopyrrole (DPP) unit, and different aromatic electron-donating end-groups were synthesized and used in organic solar cells (OSCs) to study the effect of electron-donating groups on the device performance. The three compounds, DPP-A-Ph, DPP-A-Na, and DPP-A-An, possessed intense absorption bands that covered a wide range, from 350 to 750 nm, and relatively low HOMO energy levels, from -5.50 to -5.

Synthesis and transistor properties of asymmetric oligothiophenes: relationship between molecular structure and device performance.

A series of three thiophene-naphthalene-based asymmetric oligomers-5-decyl-2,2':5',2'':5'',2'''-quaterthiophene (DtT), 5-decyl-5''-(naphthalen-2-yl)-2,2':5',2''-terthiophene (D3TN), and 5-(4-decylphenyl)-5'-(naphthalen-2-yl)-2,2'-bithiophene (DP2TN)-was synthesized by Suzuki cross-coupling reactions. The long alkyl side chains improved both the solubility of the oligomers in solvents and their tendency to self-assemble. UV/Vis absorption measurements suggested that DtT, D3TN, and DP2TN form H-type aggregates with a face-to-face packing structure.

Deep-blue phosphorescence from perfluoro carbonyl-substituted iridium complexes.

The new deep-blue iridium(III) complexes, (TF)2Ir(pic), (TF)2Ir(fptz), (HF)2Ir(pic), and (HF)2Ir(fptz), consisting of 2',4″-difluororphenyl-3-methylpyridine with trifluoromethyl carbonyl or heptafluoropropyl carbonyl at the 3' position as the main ligand and a picolinate or a trifluoromethylated-triazole as the ancillary ligand, were synthesized and characterized for applications in organic light-emitting diodes (OLEDs). Density function theory (DFT) calculations showed that these iridium complexes had a wide band gap, owing to the introduction of the strong electron withdrawing perfluoro carbonyl group. Time-dependent DFT (TD-DFT) calculations suggested that their lowest triplet excited state was dominated by a HOMO → LUMO transition and that the contribution of the metal-to-ligand charge transfer (MLCT) was higher than 34% for all four complexes, indicating that strong spin-orbit coupling exists in the complexes.

Highly efficient phosphorescent organic light emitting diodes based on iridium(III) complex with bulky substituent spacers.

We developed highly efficient phosphorescent organic light emitting diodes (PHOLEDs) using iridium(III) complex, fac-tris[4-methyl-2-2(4'-trimethylsilylphenyl)pyridine] [Ir(msippy)3]. PHOLEDs based on Ir(msippy)3 complex exhibit the yellowish-green emission with CIE color coordinates of (0.31,0.

5-Isobutyryl-2-phenylpyridine-derived iridium complexes for red phosphorescent light-emitting diodes.

For the development of efficient red materials in organic light emitting diodes, a series of cyclometalated iridium complexes with 5-isobutyryl-2-arylpyridine-derived ligands were synthesized. Complexes 1-4 exhibited red phosphorescence with quantum yields of 0.16-0.