Light-emitting organic field-effect transistor using an organic heterostructure within the transistor channel

The authors have realized a light-emitting organic field-effect transistor. Excitons are generated at the interface between a n-type and a p-type organic semiconductor heterostructure inside the transistor channel. The dimensions and the position of the p-n heterostructure are defined by photolithography. The p-n heterostructure is at a distance of several microns from the metal electrodes. Therefore, the exciton and photon quenching in this device is reduced. Numerical simulations fit well with the experimental data and show that the light-emitting zone can move within the transistor channel. (c) 2006 American Institute of Physics.status: publishe

N,N-dialkylanilines: The S1 state absorption spectrum and efficient intramolecular triplet-triplet energy transfer to an olefinic bond

Efficient intramolecular triplet-triplet energy transfer from an N,N-dialkylanilino donor to an alkene acceptor was observed in 4-(4-(propan-2-ylidene)cyclohexyl)-N,N-dimethylaniline (2) and 1-phenyl-4-cyclohexylidenepiperidine (4) using nanosecond transient absorption spectroscopy and time-resolved microwave conductivity. This enables the unequivocal assignment of the absorption spectrum of the first singlet excited state of the N,N-dialkylanilino chromophore in 4-cyclohexyl-N,N-dimethylaniline (1), 2, 1-phenyl-4-cyclohexylpiperidine (3) and 4. It has a maximum positioned between 600 and 635 nm

Broadening the absorption of conjugated polymers by "click" functionalization with phthalocyanines

Conjugated copolymer derivatives of poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) and poly(3-hexylthiophene) (P3HT) containing 10% of alkyne functionalities in the side chains have been prepared using the sulfinyl precursor route and the Rieke method, respectively. With the aim of expanding the absorption range of these conjugated polymers for their use in bulk heterojunction (BHJ) polymer:fullerene solar cells, appropriate phthalocyanine (Pc) molecules have been covalently bound through a post-polymerization "click chemistry" reaction between the alkyne functionalities in the side chains of the copolymers and a Pc functionalized with an azide moiety. The resulting poly(p-phenylenevinylene)-Pc (PPV-Pc) material holds a 9 mol% content of Pcs, while the polythiophene-Pc material (PT-Pc) contains a 8 mol% of Pc-functionalization in the side chains. As expected, the presence of the Pc contributes to the extension of the absorption up to 700 nm. BHJ solar cells have been prepared using PPV-Pc and PT-Pc materials in combination with PCBM. Although the Pc absorption contributes to the generation of photocurrent, the overall power conversion efficiencies (PCE) obtained from these cells are lower than those obtained with BHJ P3HT:PCBM (1:1) and MDMO-PPV:PCBM (1:4) solar cells. A plausible explanation could be the moderate solubility of the PPV-Pc and PT-Pc materials that limits the processing into thin films