Abstract
We report the design, synthesis, and physicochemical properties of an array of phenanthro[2,1-b:7,8-b’]dithiophene (PDT-2) derivatives by introducing five types of alkyl (CnH2n+1; n = 8, 10, 12, 13, and 14) or two types of decylthienyl groups at 2,7-positions of the PDT-2 core. Systematic investigation revealed that the alkyl length and the type of side chains have a great effect on the physicochemical properties. For alkylated PDT-2, the solubility was gradually decreased as the chain length was increased. For instance, C8-PDT-2 exhibited the highest solubility (5.0 g/L) in chloroform. Additionally, substitution with 5-decylthienyl groups showed poor solubility in both chloroform and toluene, whereas PDT-2 with 4-decylthienyl groups resulted in higher solubility. Furthermore, UV-vis absorption of PDT-2 derivatives substituted by decylthienyl groups showed a redshift, indicating the extension of their π-conjugation length. This work reveals that modification of the conjugated core by alkyl or decylthienyl side chains may be an efficient strategy by which to change the physicochemical properties, which might lead to the development of high-performance organic semiconductors.
Highlights
Since the development of the first organic field-effect transistor (OFET) in 1986, organic semiconductors have gained a great deal of attention because of their flexible, lightweight, and solution-process capable features [1]
Th2-PDT-2, introduction of Th1-PDT-2 decylthienyl groups resulted the introduction of decylthienyl groups resulted in a big increase in the energy level, i.e., to in a big increase in the highest occupied molecular orbital (HOMO) energy level, i.e., to −5.08 and −5.17 eV, respectively
The thin films of Th1-PDT-2 and Th2-PDT-2 were homogeneous and structureless. This indicated that Th1-PDT-2 and Th2-PDT-2 have better film-forming properties than those of the dialkylated PDT-2 derivatives, which are suitable for solution-processed OFETs
Summary
Since the development of the first organic field-effect transistor (OFET) in 1986, organic semiconductors have gained a great deal of attention because of their flexible, lightweight, and solution-process capable features [1]. Thebackbones incorporation of heterocycle linkages the significantly alkyl chains change and conjugated and or heteroatom-containing side between chains could the energy backbones or heteroatom-containing side chains could significantly change the energy levels and levels and molecular packing. The former is the introduction of alkylthienyl groups, which can increase molecular packing. The former is the introduction of alkylthienyl groups, which can increase the the solubility and highest occupied molecular orbital (HOMO) energy levels. 2,7-positions of the PDT-2 core may control crystallinity, solubility, and HOMO energy level, leadingto improved transistor properties.
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