Molecular Engineering of C₆₀-Based Conjugated Oligomer Ensembles:  Modulating the Competition between Photoinduced Energy and Electron Transfer Processes

Abstract

A series of novel and soluble C60-(pi-conjugated oligomer) dyads were synthesized, starting from suitably functionalized oligomer precursors (i.e., dihexyloxynaphthalene, dihexyloxynaphthalene-thiophene, and dihexyloxybenzene-thiophene). A systematic change in the nature of the oligomeric component allowed (i) tailoring the light absorption of the chromophore by shifting the ground-state absorption from the ultraviolet to the visible region and (ii) varying the oxidation potential of the donor. The resulting electro- and photoactive dyads were examined by electrochemical and photophysical means. In general, both singlet-singlet energy transfer and intramolecular electron transfer were found to take place and, most importantly, to compete with each other in the overall deactivation of the photoexcited oligomer. The selection of polar solvents in combination with the dihexyloxybenzene-thiophene donor shifted the reactivity from an all energy (1a; dihexyloxynaphthalene) to an all electron-transfer scenario (1d, dihexyloxybenzene-thiophene). Encouraged by the favorable electron-transfer properties of dyad 1d, we prepared photodiodes by embedding 1d between asymmetric metal contacts, which showed external monochromatic efficiencies (IPCE) close to 10% at the maximum absorption of the molecule.

Synthesis, Photophysics, and Photoresponse of Fullerene‐Based Azoaromatic Dyads

“…[26] The different values of the open-circuit voltage (V oc ) could be justified either by different energetics of the materials, as it occurs in the case of polymer-fullerene-blended devices, [40] or by different shunt effects. Rather low values [22,24,41,42] are quite low, if compared with those usually published for blended cells. [15] In general, an increasing series resistance and a decreasing shunt resistance tend to reduce the fill factor, although other factors related to the diode properties and/or the material transport properties, cannot be ruled out.…”

“…Other promising approaches include the use of molecular dyads and triads made of a functionalized fullerene covalently linked to oligomeric, conjugated architectures. [21][22][23][24][25] Such cells gave power conversion efficiencies ranging from approximately 0.02 % to our recently reported 0.37 %, under 80 mW cm…”

Single Material Solar Cells: the Next Frontier for Organic Photovoltaics?

“…Guldi et al analyzed the photovoltaic properties of a dyad with a terminal bromothiophene ( 8 ). [ 49 ] A single layer device ITO/ PEDOT-PSS/ 8 /LiF/Al gave a J sc of 0.75 mA cm − 2 , a V oc of 0.67 V, and a PCE of ca 0.20%. A dyad molecule composed of covalently linked zinc phthalocyanine and C 60 ( 9 ) has been synthesized by Loi et al [ 50 ] A SMOC was fabricated by sandwiching a fi lm spin-cast from a toluene solution between ITO/PEDOT-PSS and LiF-Al electrodes.…”

Solid Film versus Solution‐Phase Charge‐Recombination Dynamics of exTTF–Bridge–C60 Dyads

“…A further Rosemund-von Braun reaction with copper(i) cyanide in DMF, followed by treatment with ammonia, led to the dicyano derivative 6 [38] . Compound 6 underwent a reduction process with DIBAL-H and hydrolysis to form dialdehyde 7.…”