Room temperature excitonic coupling in self-assembled copper – Fullerene hybrid films exposed to ambient air

Abstract

Analytically sound combination of organic and inorganic semiconductors in designing functional hybrid nanomaterials promises new advances in nanoscience and in creation of next-generation optoelectronic devices. In this work, we report on combining two contrasting semiconductors (inorganic and organic) possessing attractive optical and electronic properties, namely Cu2O (in form of small single-crystalline nanoparticles, NPs) and C60-fullerene (as a medium supporting the NP ensemble), which were formed within the well-controlled Cux(Oy)C60 hybrid films through self-assembling and ambient air exposure of the vapour-deposited Cu and C60 mixture. The controllability of the hybrid film nanostructure was established and verified through systematic study of the films using Rutherford backscattering spectrometry, transmission electron microscopy, X-ray diffraction, Raman spectrometry and spectroscopic ellipsometry. The remarkable coincidence of the optical absorption peaks around 3.5 eV, reported for the Wannier-Mott (WM) excitons in a Cu2O crystal and detected for the Frenkel (F) excitons in the pristine C60 film, allowed us to observe room temperature polaritons as a product of the F-WM excitonic strong coupling. Quite high coupling energy of the FWM hybrid exciton estimated for the Cux(Oy)C60 films in the x interval of 5 < x < 15 (from 390 meV to 610 meV) implies the mediated effect of nanocavity photons and quantum confinement effect, strongly enhancing the hybrid exciton coupling energy. The implemented study discloses the self-assembled Cux(Oy)C60 hybrid films as promising material for application in optoelectronics and nonlinear optics.