A supramolecular "double-cable" structure with a 129 44 helix in a columnar porphyrin-c 60 dyad and its application in polymer solar cells
Journal
Advanced Energy Materials
Journal Volume
2
Journal Issue
11
Pages
1375
Date Issued
2012-11-01
Author(s)
Zhang, Wen Bin
Sun, Hao Jan
Van Horn, Ryan M.
Kulkarni, Rahul R.
Tsai, Chi Chun
Hsu, Chain Shu
Lotz, Bernard
Gong, Xiong
Cheng, Stephen Z.D.
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. © 2012 WILEY-VCH Verlag GmbH & Co.
Type
journal article