Photoluminescence spectroscopy of pure pentacene, perfluoropentacene and mixed thin films

TL;DR

This study investigates the temperature-dependent photoluminescence spectra of pure and mixed pentacene and perfluoropentacene thin films, revealing coupling effects and charge-transfer phenomena in the blend through experimental and theoretical analysis.

Contribution

It provides new insights into the optical transitions and coupling effects in PEN, PFP, and their blends using combined experimental PL spectra and TD-DFT calculations.

Findings

Observation of a 1.4 eV PL transition in the mixed film indicating coupling.

Comparison of PL spectra with existing literature for PEN and new findings for PFP.

Evidence of charge-transfer effects in the blend.

Abstract

We report detailed temperature dependent photoluminescence (PL) spectra of pentacene (PEN), perfluoropentacene (PFP), and PEN:PFP mixed thin films grown on SiO2. PEN and PFP are particularly suitable for this study, since they are structurally compatible for good intermixing and form a model donor/acceptor system. The PL spectra of PEN are discussed in the context of existing literature and compared to the new findings for PFP. We analyze the optical transitions observed in the spectra of PEN and PFP using time-dependent density functional theory (TD-DFT) calculations. Importantly, for the mixed PEN:PFP film we observe an optical transition in PL at 1.4 eV providing evidence for coupling effects in the blend. We discuss a possible charge-transfer (CT) and provide a tentative scheme of the optical transitions in the blended films.