Stereoisomer-dependent conversion of dinaphthothienothiophene precursor films

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–H$$\cdots$$ ⋯ O 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.

Quantitative Analysis of Photochemical Reactions in Pentacene Precursor Films

“…The band assignments were based on density functional theory (DFT) calculations using Gaussian 16 software with B3LYP/6-31G­(d,p) as the basis set. The calculated wavenumber was linearly scaled in accordance with previous reports. , …”

“…The calculated wavenumber was linearly scaled in accordance with previous reports. 17,27 2D-GIXD Measurements. 2D-GIXD measurements were performed using a Rigaku (Tokyo, Japan) SmartLab diffractometer, equipped with a HyPix-3000 two-dimensional image detector.…”

“…They proposed a model in which the additive molecules remain in the precursor film after spin coating to form a semidry film, and the semidry state is essential for promoting the conversion reaction. This model is acceptable considering that solid-state reactions generally require high-thermal energy and a long period of time to proceed. − …”

“…In addition, an optically isotropic (OI) spectrum, which is a molecular-orientation free spectrum, is also obtained by simply averaging the IP and OP spectra . Since the band intensity of the OI spectrum is proportional only to the quantity of chemical species, the quantitative analysis of chemical reactions can be accurately performed. ,, IR spectroscopy has another powerful benefit for detecting trace molecules irrespective of the crystallinity, , such as impurities, including residual solvents.…”

“…11 Since the band intensity of the OI spectrum is proportional only to the quantity of chemical species, the quantitative analysis of chemical reactions can be accurately performed. 11,17,23 IR spectroscopy has another powerful benefit for detecting trace molecules irrespective of the crystallinity, 10,24 such as impurities, including residual solvents.…”