Stabilizing Bicontinuous Nanophase Segregation in πCP−C₆₀ Donor−Acceptor Blends

Abstract

The synthesis and thin film properties of a conjugated polymer bearing graft chains that are compatible with a fullerene, chemically modified with a similar motif, are described. The graft copolymer, obtained by nitroxide-mediated radical polymerization of a vinyl triazole onto a postfunctionalized poly(3-hexylthiophene) (P3HT) backbone, is blended with a fullerene modified with a pendant triazole functionality (TAZC60). For a given ratio of polymer:TAZC60, graft copolymer (P3HT-g-PVTAZ:TAZC60) blends exhibit substantially reduced photoluminescence compared to P3HT:TAZC60 blends, while TEM analysis reveals the graft polymer undergoes extensive mixing with the fullerene to form bicontinuous 10 nm phase domains. Graft polymer blends annealed for 1 h at 140 degrees C retain their nanometer phase separation as evidenced by TEM, UV-vis, XRD, and photoluminescence analysis, and phase purity was enhanced. In contrast, P3HT:TAZC60 blends exhibit micron-sized phase-segregated morphologies before and after annealing. The chemical similarity of the triazole functionality attached to P3HT and the fullerene leads to the formation of films with uniform, stable, nanophase morphologies. This strategy may prove a useful strategy for controlling the extent of phase segregation in electron donor and acceptor blends of pi-conjugated polymers (piCPs) and fullerenes.

Effective Use of Electrically Insulating Units in Organic Semiconductor Thin Films for High‐Performance Organic Transistors

“…Compared with the p-type block copolymers, relatively few results are available for n-type block copolymers, possibly due to the difficulty of the synthetic method based on n-type conjugated backbones. [143][144][145][146][147][148][149][150][151][152][153][154][155][156][157][158][159][160][161] However, a study on donor-acceptor rod-coil diblock copolymers of P3HT and poly(2-phenyl-5-(4-vinylphenyl)-1,3,4-oxadiazole) (POXD) showed that the incorporation of the POXD acceptor would reduce the degree of order of P3HT leading to lower field-effect mobilities. [137,[142][143][144] Huettner et al synthesized a diblock copolymer consisting of poly(perylene bisimide acrylate) and PS.…”

A New Supramolecular Route for Using Rod‐Coil Block Copolymers in Photovoltaic Applications

“…Three absorption peaks located at 519, 555, and 603 nm can be seen and are similar to the spectral features frequently observed in rr-P3HT thin films. [42,43] The P3HT absorption peaks are known to be related to the vibronic splitting of the p-p* transition, and their amplitude ratio has been correlated before to the degree of polymer ordering. Their presence in the absorption spectra reflects a significant degree of structural ordering, which increases upon annealing, even for relatively high fullerene volume fractions (up to 36%).…”

Altering the Thermodynamics of Phase Separation in Inverted Bulk‐Heterojunction Organic Solar Cells

“…[1,2] These solar cells, based on organic semiconductors, are often designed to have a bulk-heterojunction-type architecture in which the photoactive layer consists of an interpenetrating network of an electron donor and an acceptor. [3][4][5] The morphological details of the photoactive layer has dramatic consequences on device performance; having high interfacial area between domains of the electron donor and acceptor can enhance exciton dissociation. [6][7][8] On the other hand, if the domains of electron donor and acceptor within the photoactive layer are too fine and the interfacial area between the two species too high, charge recombination can dominate.…”