Many-body hybrid Excitons in Organic-Inorganic van der Waals Heterostructures

TL;DR

This study reports the discovery of hybrid excitons at the organic-inorganic CuPc/MoSe2 interface, demonstrating their tunability via molecular orientation and potential for advanced many-body exciton physics.

Contribution

It provides experimental and theoretical evidence of hybrid excitons at the organic-inorganic interface, highlighting their unique properties and tunability, which were previously unexplored.

Findings

Hybrid excitons observed at CuPc/MoSe2 interface.

Strong hybridization between CuPc LUMO and MoSe2 conduction band.

Hybrid excitons exhibit signatures of both Frenkel and Wannier-Mott types.

Abstract

The coherent many-body interaction at the organic-inorganic interface can give rise to intriguing hybrid excitons that combine the advantages of the Wannier-Mott and Frenkel excitons simultaneously. Unlike the 2D inorganic heterostructures that suffer from moment mismatch, the hybrid excitons formed at the organic-inorganic interface have a momentum-direct nature, which have yet to be explored. Here, we report hybrid excitons at the copper phthalocyanine/molybdenum diselenide (CuPc/MoSe2) interface with strong molecular orientation dependence using low-temperature photoluminescence spectroscopy. The new emission peaks observed in the CuPc/MoSe2 heterostructure indicate the formation of interfacial hybrid excitons. The density functional theory (DFT) calculation confirms the strong hybridization between the lowest unoccupied molecular orbital (LUMO) of CuPc and the conduction band minimum (CBM) of MoSe2, suggesting that the hybrid excitons consist of electrons extended in both layers and holes confined in individual layers. The temperature-dependent measurements show that the hybrid excitons can gain the signatures of the Frenkel excitons of CuPc and the Wannier-Mott excitons of MoSe2 simultaneously. The out-of-plane molecular orientation is used to tailor the interfacial hybrid exciton states. Our results reveal the hybrid excitons at the CuPc/MoSe2 interface with tunability by molecular orientation, which suggests that the emerging organic-inorganic heterostructure can be a promising platform for many-body exciton physics.