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Buta-1,3-diyne-Based π‑Conjugated Polymers for Organic Transistors and Solar Cells
journal contribution
posted on 2017-02-09, 20:35 authored by Brian
J. Eckstein, Ferdinand S. Melkonyan, Nanjia Zhou, Eric F. Manley, Jeremy Smith, Amod Timalsina, Robert P. H. Chang, Lin X. Chen, Antonio Facchetti, Tobin J. MarksWe
report the synthesis and characterization of new alkyl-substituted
1,4-di(thiophen-2-yl)buta-1,3-diyne (R-DTB) donor building blocks,
based on the −CC–CC– conjugative
pathway, and their incorporation with thienyl-diketopyrrolopyrrole
(R′-TDPP) acceptor units into π-conjugated PTDPP-DTB
polymers (P1–P4). The solubility
of the new polymers strongly depends on the DTB and DPP solubilizing
(R and R′, respectively) substituents. Thus, solution processable
and high molecular weight PDPP-DTB polymers are achieved for P3 (R = n-C12H25, R′
= 2-butyloctyl) and P4 (R = 2-ethylhexyl, R′ =
2-butyloctyl). Systematic studies of P3 and P4 physicochemical properties are carried using optical spectroscopy,
cyclic voltammetry, and thermal analysis, revealing characteristic
features of the dialkynyl motif. For the first time, optoelectronic
devices (OFETs, OPVs) are fabricated with 1,3-butadiyne containing
organic semiconductors. OFET hole mobilities and record OPV power
conversion efficiencies for acetylenic organic materials approach
0.1 cm2/(V s) and 4%, respectively, which can be understood
from detailed thin-film morphology and microstructural characterization
using AFM, TEM, XRD, and GIWAXS methodologies. Importantly, DTB-based
polymers (P3 and P4) exhibit, in addition
to stabilization of frontier molecular orbitals and to −CC–CC–
relief of steric torsions, discrete morphological pliability through
thermal annealing and processing additives. The advantageous materials
properties and preliminary device performance reported here demonstrate
the promise of 1,3-butadiyne-based semiconducting polymers.