Charge Transfer Exciton at Hybrid Organic-2d Inorganic Heterointerface

The low dimensionality and van der Waals nature of organics and transition metal dichalcogenides (TMDs), provides a unique opportunity to combine two disparate excitonic systems without elemental diffusion. Such hybrid interfaces can be engineered to demonstrate photophysical properties that do not normally coexist in the individual material systems.<br/>In this work, we use advanced optical spectroscopy to investigate hybrid type-II heterointerface formed between monolayer tungsten disulfide (WS₂) and Tris(4-(5-phenylthiophen-2-yl)phenyl)amine (TPTPA) dispersed in a crystalline rubrene matrix. We study the hybrid charge transfer excitons (HCTEs) formed between TPTPA and WS₂ and find that the TPTPA molecules, embedded in orthorhombic rubrene crystalline structure are aligned with specific orientations. Furthermore, the dipole orientation of TPTPA molecules rotates with the rubrene single crystal domain. Such orientation control enables us to systematically study the HCTE dynamics and we find that the formation efficiency is dependent on the twist angle between the monolayer and TPTPA orientation. Finally, circular dichroism measurements reveal that HCTEs preserve the valley (K an K') pseudospin information of the WS₂ monolayer in spite of the charge transfer process at the interface. The results provide new insights into the charge transfer dynamics at hybrid interfaces that can directly influence future applications in energy conversion, sensing and on-chip data communication and processsing.