Search

Silicon nano-particles grafted with two different organic oligomers were prepared; the oligomers used were a phenylene-vinylene (PV) oligomer and a 3,3'''-didodecylquaterthiophene. The graftings were performed by the use of two different functional groups, the PV oligomer was grafted by a hydroxyl-group in the form of a phenol and a lithium derivative was used to graft the 3,3'''-didodecylquaterthiophene. The morphology and size of the grafted particles were analyzed by atomic force microscopy (AFM) and the extent of the grafting was analyzed by NMR. Organic photovoltaics with normal geometry (ITO/PEDOT:PSS/active layer/Al) were prepared using these materials as a donor and phenyl-C61-butyric acid methyl ester ([60]PCBM) as the acceptor and yielded a power conversion efficiency (PCE) of 0.27%, an open circuit voltage (VOC) of 0.93 V, a short circuit current density (JSC) of 0.89 mA/cm², and a fill factor (FF) of 32.5% for a lead device with an active area of 0.25 cm&#178. [ABSTRACT FROM AUTHOR]

Controlling the size of the oligomer and introducing functional groups at the ends of the oligomer that allow it to react with separate electrodes are critical issues when preparing materials for molecular wires. We demonstrate a general synthetic approach to oligophenylenevinylene (OPV) derivative molecules with a molecular length up to 9-10 nm which allow for the introduction of aromatic thioacetate functionality in fully conjugated oligomer systems. Oligomers containing 3-15 phenyl units were synthesized by step wise Horner-Wadsworth-Emmons (HWE) reactions of a bifunctional OPV-monomer, which demonstrated good control of the size of the OPVs. Workup after each reaction step ensures a high purity of the final products. End group functionalization was introduced as a last step. [ABSTRACT FROM AUTHOR]

A new stepwise directional synthetic route to single-oligomer p-phenylenevinylenes (OPVs) has been developed. The first step in the reaction sequence is the condensation of a functionalized benzaldehyde with a novel monomer having a methyl phosphonate ester group in one end and an acetal-protected aldehyde at the other end of a stilbene core. Oligomerization then proceeds stepwise by alternating reaction of the previous aldehyde-terminated OPV fragment with the monomer and deprotection of the acetal. Thus, a series of OPVs with 3, 5, 7, 9, and 11 phenylene vinylene units has been prepared that has an electron-donating methoxy group at one end and an electron-accepting aldehyde group at the other end. Some examples where a dimethylamino group replaced the methoxy group were also prepared. The oligomer with seven phenylene vinylene units was then further derivatized at the aldehyde position to create a series of OPVs with a range of substituents from strongly electron-accepting nitrophenyl to electron-donating methoxyphenyl. Photovoltaic cells were assembled with the synthesized OPVs as the photoactive layer. Illumination under simulated sunlight (AM1.5) gave short circuit currents (Isc) in the range 0.015-0.5 mA cm-2 and typical open circuit voltages (Voc) of 0.4-0.8 V. The maximum efficiency obtained was ∼0.1%. [ABSTRACT FROM AUTHOR]