Polymorphic Phase-Dependent Optical and Electrical Properties of a Diketopyrrolopyrrole-Based Small Molecule
dataset
posted on 2016-07-19, 00:00 authored by Shabi Thankaraj Salammal, Zhongqiang Zhang, Jiehuan Chen, Basab Chattopadhyay, Jiake Wu, Lei Fu, Congcheng Fan, Hongzheng ChenFour different polymorphic conformations
of diethyl 5,5′-[5,5′-[2,5-bis(2-ethylhexyl)-3,6-dioxo-2,3,5,6-tetrahydropyrrolo[3,4-c]pyrrole-1,4-diyl]bis(thiophene-5,2-diyl)]difuran-2-carboxylate
(DPP-(CF)2), namely, DPP-(CF)2-α, DPP-(CF)2-β, DPP-(CF)2-γ, and DPP-(CF)2-ω, were identified from X-ray diffraction analysis conducted
on their thin films and single crystals. Highly crystalline and well-textured
thin films of these four polymorphs were successfully prepared via
postgrowth solvent vapor and thermal annealing treatments to investigate
the polymorphic phase-dependent optical and electrical properties
of DPP-(CF)2. Interestingly, during the phase transition
from DPP-(CF)2-α to DPP-(CF)2-ω,
the optical band gap decreases from 1.75 to 1.5 eV because of the
enhanced π–π interaction between the neighboring
molecules. Except for DPP-(CF)2-γ, the other three
phases show ambipolar charge transport. Although DPP-(CF)2-β and DPP-(CF)2-γ exhibit a similar way of
packing, a small increment in the π–π-stacking
distance (0.006 Å) and twist conformation of the grafted electron-donating
moieties of DPP-(CF)2-γ are found to reduce its hole
mobility.
