Addition of dihydromethano group to fullerenes to improve the performance of bulk heterojunction organic solar cells.

Adding a compact dihydromethano (CH2 ) group to a 58π-indene fullerene (C60 (Ind)) creates a 56π-electron dihydromethano/indene fullerene (C60 (CH2 )(Ind)) and raises the LUMO level with only a minimal increase in size. This class of compounds features reduced conjugation that raises the LUMO level, and a high electron mobility because of the small CH2 addend.

α,α'-Diarylacenaphtho[1,2-c]phosphole P-oxides: divergent synthesis and application to cathode buffer layers in organic photovoltaics.

A divergent method for the synthesis of α,α'-diarylacenaphtho[1,2-c]phosphole P-oxides has been established; α,α'-dibromoacenaphtho[c]phosphole P-oxide, which was prepared through a Ti(II)-mediated cyclization of 1,8-bis(trimethylsilylethynyl)naphthalene, underwent a Stille coupling with three different kinds of aryltributylstannanes to afford the α,α'-diarylacenaphtho[c]phosphole P-oxides in moderate to good yields. X-ray crystallographic analyses and UV/Vis absorption/fluorescence measurements have revealed that the degree of π-conjugation, the packing motif, the electron-accepting ability, and the thermal stability of the acenaphtho[c]phosphole π-systems are finely tunable with the α-aryl substituents. All the P=O and P=S derivatives exhibited high stability in their electrochemically reduced state. To use this class of arene-fused phosphole π-systems as n-type semiconducting materials, we evaluated device performances of the bulk heterojunction organic photovoltaics (OPV) that consist of poly(3-hexylthiophene), an indene-C(70) bisadduct, and a cathode buffer layer. The insertion of the diarylacenaphtho[c]phosphole P-oxides as the buffer layer was found to improve the power conversion efficiency of the polymer-based OPV devices.

Bis(methylthio)tetracenes: synthesis, crystal-packing structures, and OFET properties.

5,12-Bis(methylthio)tetracene (2) and 5,11-bis(methylthio)tetracene (3) were synthesized. DFT calculations indicate that the HOMO and LUMO energy levels of 2 and 3 are lowered by 0.13-0.24 eV and their HOMO-LUMO energy gaps are reduced by 0.1 eV relative to those of tetracene. X-ray crystallographic data revealed that 2 is arranged as a result of a 1-D slipped-cofacial π-stacking with S-S and S-π interactions, similar to the packing arrangement of 6,13-bis(methylthio)pentacene (1), whereas 3 exhibits a herringbone packing arrangement without S-S interactions. The OFET devices fabricated using spin-coated films of soluble 1 and 2, with a bottom-contact device configuration, exhibited hole mobilities as high as 1.3 × 10(-2) and 4.0 × 10(-2) cm(2) V(-1) s(-1) with current on/off ratios of over 10(5) and 10(4), respectively.

2,3-disubstituted benzofuran and indole by copper-mediated C-C bond extension reaction of 3-zinciobenzoheterole.

[reaction: see text] A metalative 5-endo-dig cyclization reaction of 2-ynylphenoles or anilines effected by BuLi and ZnCl(2) produces 3-zinciobenzoheteroles in excellent yield. These intermediates have been transmetalated to the corresponding cuprates and allowed to react with electrophiles to produce a variety of 2,3-disubstituted benzofurans and indoles.