A Theoretical Study on the Temperature Control of Fabrication of Pentacene Thin Film Transistors from Soluble Pentacene Precursors

It is possible to prepare pentacene thin films using retro Diels-Alder reaction of soluble precursors. There are a variety of leaving groups for the precursors with different temperatures of conversions to pentacene. We conducted a theoretical analysis of the formation mechanism of pentacene from several reported precursors at the B3LYP/6-31G* level of theory to clarify the relationship between the conversion temperature and the leaving group. Results from our calculations showed a low activation energy results in a low temperature for the conversion. The PLS analysis confirmed that the magnitude of Ea values are well correlated with heat of reactions and energy levels of LUMO for the leaving groups. In order to confirm why conversion temperatures are dependent on solvents used for fabrications of pentacene thin films, changes in activation energies were investigated for retro Diels-Alder reactions of the precursors including MeOH. It was calculated that the activation energies for these systems were lower by 0.7 kcal mol-1 than those without MeOH molecules. This trend is consistent with that observed. The present theoretical results suggested that we can control the temperatures of the pentacene conversion by choosing proper bridging reagents as well as the solvent for thin film fabrications from the precursors.