Analysis of optical and electronic properties of pentacene for application in organic transistors and photoresistors

Results of a quantum chemical analysis of the spectral and electronic characteristics of a pentacene molecule, one of the most promising organic semiconductors, are presented. The calculations are performed using the TD-DFT method and the Gaussian software package. The first six excited states of pentacene are analyzed in order to identify the most effective photoactive transitions. Key parameters are computed, including the excitation energy, absorption wavelength, oscillator strength, dipole moment, rotational strength, and the energy gap between the HOMO and LUMO orbitals. It is shown that the first excited state (S1) is characterized by a low excitation energy (1.6560 eV), an absorption wavelength of 748.71 nm (near-infrared range), and a relatively high oscillator strength (0.0375), which indicates effective absorption of near-infrared radiation. The excited states S2—S6 exhibit significantly weaker absorption, mainly in the ultraviolet region of the spectrum. Analysis of the HOMO—LUMO gap indicates significant electron delocalization and a small energy gap, contributing to efficient charge transfer. It is established that the electric dipole moment is oriented predominantly along the Y axis, which may be of practical importance for devices operating with polarized radiation. In general, the results obtained confirm the expediency of using pentacene as an active material for organic photosensitive electronic devices and allow to identify areas for further optimization, including control of molecular orientation.

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