Electronic Spectra of C₆₀ Films Using Screened Range Separated Hybrid Functionals

Area of Science:

• Computational materials science
• Quantum chemistry
• Solid-state physics

Background:

• Understanding the electronic properties of C60 thin films is crucial for advanced material applications.
• Accurate theoretical prediction of electronic spectra, especially excitation energies, remains a challenge.

Purpose of the Study:

• To computationally investigate the electronic spectra of C60 thin films.
• To validate a new density functional theory (DFT) framework for condensed phase systems.
• To analyze and assign spectral features, including excitonic effects.

Main Methods:

• Utilized a density functional theory (DFT) framework combining a screened range separated hybrid (SRSH) functional with a polarizable continuum model (PCM).
• Calculated electronic excitation energies using time-dependent DFT (TD-DFT).
• Investigated excitonic effects to interpret spectral features.

Main Results:

• The SRSH-PCM approach accurately correlated frontier orbital energies with condensed-phase ionization potential and electron affinity.
• Calculated excited states successfully reproduced experimental spectral peaks between 3.6–4.6 eV.
• Identified and assigned a low-lying spectral peak at 2.7 eV to an excitonic state, also reproducing red-shifted features.

Conclusions:

• The SRSH-PCM DFT approach provides high-quality electronic excitation energies for condensed-phase systems like C60 thin films.
• The study successfully explains the main experimental spectral features of C60 thin films, including excitonic contributions.
• This computational method offers a reliable tool for predicting the electronic spectra of molecular materials.