Abstract
Soluble precursor materials of organic semiconductors are employed for fabricating solution-processable thin film devices. While the so-called precursor approach has already been tried for various organic electronic devices such as transistors and solar cells, understanding of the conversion process in the film lags far behind. Here, we report that molecular aggregation of the precursor compound significantly influences the thermal conversion reaction in the film. For this study, two stereoisomers of a dinaphthothienothiophene (DNTT) precursor that are the endo- and exo-DNTT-phenylmaleimide monoadducts are focused on. The structural change during the thermal conversion process has been investigated by a combination of infrared spectroscopy and X-ray diffraction techniques. The results show that the endo-isomer is readily converted to DNTT in the film by heating, whereas the exo-isomer exhibits no reaction at all. This reaction suppression is found to be due to the self-aggregation property of the exo-isomer accompanying the intermolecular C–HcdotsO interactions. This finding shows a new direction of controlling the on-surface reaction, as well as the importance of analyzing the film structure at the initial stage of the reaction.
Highlights
Soluble precursor materials of organic semiconductors are employed for fabricating solutionprocessable thin film devices
Considering that the chemical conversion proceeds as a solid-phase reaction, the molecular aggregation of the precursor compound before the thermal treatment should influence the efficiency of the chemical reaction
The conversion reaction with the precursor approach would be controlled by changing the aggregation structure of the precursor compound in the film
Summary
Soluble precursor materials of organic semiconductors are employed for fabricating solutionprocessable thin film devices. The results show that the endo-isomer is readily converted to DNTT in the film by heating, whereas the exoisomer exhibits no reaction at all This reaction suppression is found to be due to the self-aggregation property of the exo-isomer accompanying the intermolecular C–H· · · O interactions. On-surface synthesis has emerged as a promising approach for preparing two-dimensional nanosheet structures such as covalent organic frameworks and graphene n anoribbons[1–4] This solid-state reaction-based technique is important for synthesis of compounds that cannot be produced in solution, as found for linear acenes fused with seven or more benzene r ings[5]. According to the original p apers[9,10], exo-DPM has a lower solubility in common organic solvents than endo-DPM This suggests that the exo-isomer takes a tighter packing in a solid sample than the endo-isomer, and the difference in the aggregation structure would have a significant impact on the conversion reaction to DNTT. The difference of the on-surface conversion reaction, has not been studied so far
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