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A series of oligo(N-methylaniline)s consisting of alternating meta and para substituted benzene rings up to 8 units has been synthesized via palladium-catalyzed coupling reactions. These oligo(N-methylaniline)s can be oxidized reversibly to the corresponding oligo(cation radical)s, which are stable at ambient temperature and possess a high-spin ground state as evidenced by ESR spectroscopy.

Oligo(phenyleneethynylene)s with pendant p-phenylenediamine groups have been synthesized via palladium-catalyzed coupling reactions. These oligo(phenyleneethynylene)s can be reversibly oxidized to the corresponding di(radical cation)s, which are stable at ambient temperature and have a high-spin state as determined by temperature-dependent ESR spectroscopy.

A novel low-bandgap conjugated polymer (PTPTB, E g = ∼ 1.6 eV), consisting of alternating electron-rich N-dodecyl-2,5-bis(2'-thienyl)pyrrole (TPT) and electron-deficient 2,1,3-benzothiadiazole (B) units, as a donor material is studied together with a soluble fullerene derivative (PCBM) as acceptor to prepare bulk heterojunction photovoltaic cells. Photoinduced absorption (PIA) and fluorescence spectroscopy on blends of PTPTB and PCBM gave direct spectral evidence of the photogeneration of a charge-separated state. Preliminary results on photovoltaic cells prepared using thin PTPTB:PCBM films as an active layer, sandwiched between ITO/PEDOT:PSS and Al electrodes, showed promising characteristics.

The photoluminescence of supramolecular assemblies of two lengthy oligothiophenes having eleven and seventeen repeat units that are end-substituted with third generation poly(benzyl ether) dendritic wedges, G3-T11-G3 and G3-T17-G3 respectively, is presented. Recent thermochromism studies revealed that these novel materials form nanoscale aggregates in solution. Variable temperature photoluminescence measurements confirm the complete transformation of a molecularly dissolved phase into an aggregated phase within a rather narrow temperature regime.

Novel tailor-made AB, ABAC, and ABAA type heteroaromatic copolymers, in which B represents an N-alkylpyrrole unit, were synthesized via Pd-catalyzed Stille polymerization and characterized by a variety of analytical techniques. MALDI-TOF mass spectrometry allowed the detailed characterization of polymer weight and determination of end groups. By varying the nature of the repeating monomer units and their sequence, copolymers with promising properties for photovoltaic devices could be obtained.

In this work we present efficiency data of solar cells based on mixtures from soluble alkoxy PPV, a highly soluble fullerene derivative (PCBM) and three different conventional, non conjugated polymers, polystyrene (PS), polyvinylcarbazole (PVK) and polyvinylbenzenechlorid (PVBC). We studied the I/V characteristics of devices with various amounts of conventional polymer. Energy conversion efficiency ¿e and carrier collection efficiencies ¿c are calculated for these three composite devices and compared with the data for a pure conjugated polymer / fullerene device. We find that addition of up to 10% of conventional polymer to the electroactive composite is possible without lowering the efficiency of the device.

Results of controlled degradation experiments performed with the individual components and with the actual mixture used in plastic solar cells are shown. A testing procedure for the stability and for degradation effects under illumination in controlled atmosphere using FTIR-ATR spectroscopy is presented. The method yields rapid information on the degradation processes on molecular level within a few hours.

EPR spectroscopy is used to characterize a novel triplet ground state diradical obtained from oxidation of 1,3-phenylene-bis{[(4-t-butylphenyl)methylene]triphenyl phosphorane}.

Three-electron oxidation of N,N′,N″ -tris[4-(diphenylamino)phenyl]- N,N′,N″ '-triphenyl-13,5-berizenetriamine produces the corresponding tri(cation radical). EPR and UV/Vis/NIR spectroscopy show that this tri(cation radical) is stable at room temperature and possesses a quartet ground state.

We present spectral evidence for the formation of triplet-state photoexcitations in T7 films and solutions. Introduction of C60 affects the photophysical processes dramatically via electron transfer (film) or energy transfer (solution) from photoexcited T7 to C60.