A supramolecular "double-cable" structure with a 129 44 helix in a columnar porphyrin-c 60 dyad and its application in polymer solar cells

Chien-Lung Wang*, Wen Bin Zhang, Hao Jan Sun, Ryan M. Van Horn, Rahul R. Kulkarni, Chi Chun Tsai, Chain-Shu Hsu, Bernard Lotz, Xiong Gong, Stephen Z.D. Cheng

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

38 Scopus citations

Abstract

A novel porphyrin-C 60 dyad (PCD1) is designed and synthesized to investigate and manipulate the supramolecular structure where geometrically isotropic [such as [60]fullerene (C 60 )] and anisotropic [such as porphyrin (Por)] units coexist. It is observed that PCD1 possesses an enantiomeric phase behavior. The melting temperature of the stable PCD1 thermotropic phase is 160 ° C with a latent heat ( H ) of 18.5 kJ mol - 1 . The phase formation is majorly driven by the cooperative intermolecular Por-Por and C 60 -C 60 interactions. Structural analysis reveals that this stable phase possesses a supramolecular "double-cable" structure with one p -type Por core columnar channel and three helical n -type C 60 peripheral channels. These "double-cable" columns further pack into a hexagonal lattice with a = b = 4.65 nm, c = 41.3 nm, a = β = 90 ° , and = 120 ° . The column repeat unit is determined to possess a 129 44 helix. With both donor (D; Pro) and acceptor (A; C 60 ) units having their own connecting channels as well as the large D/A interface within the supramolecular "double-cable" structure, PCD1 has photogenerated carriers with longer lifetimes compared to the conventional electron acceptor [6,6]-phenyl-C 61 -butyric acid methyl ester. A phase-separated columnar morphology is observed in a bulk-heterojunction (BHJ) material made by the physical blend of a low band-gap conjugated polymer, [poly[2,6-(4,4-bis-(2- ethylhexyl)-4 H -cyclopenta [2,1-b;3,4-b ' ]-dithiophene)- alt -4,7-(2,1,3-benzothiadiazole)] (PCPDTBT), and PCD1. With a specifi c phase structure in the solid state and in the blend, PCD1 is shown to be a promising candidate as a new electron acceptor in high performance BHJ polymer solar cells.

Original languageEnglish
Pages (from-to)1375-1382
Number of pages8
JournalAdvanced Energy Materials
Volume2
Issue number11
DOIs
StatePublished - 1 Nov 2012

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