Orientation Dependent Interlayer Coupling in Organic–Inorganic Heterostructures

• Published in: Advanced functional materials Vol. 34; no. 28
• Main Authors: Bartlam, Cian, Saigal, Nihit, Heiserer, Stefan, Lambers, Hendrik, Wurstbauer, Ursula, Duesberg, Georg S.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 01-07-2024
• Subjects: 2D materials; Alignment; Bilayers; Charge transfer; Coupling (molecular); Excitation spectra; Excitons; Heterostructures; Hybrid systems; interlayer excitons; Interlayers; Molybdenum disulfide; MoS2; Optical properties; Optoelectronic devices; Organic chemistry; Orientation; perylene; Photoluminescence; Raman spectroscopy; Scanning probe microscopy; self‐assembly; Spectrum analysis; Temperature dependence; Transition metal compounds
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202315302

Organic–inorganic 2D heterostructures combine the high optical absorption of organic molecules with exciton‐dominated optical properties in layered transition metal dichalcogenides (TMDs) such as MoS2. Critical to the interaction and the optical response in such hybrid systems is the electronic band alignment at the interface between the two species. Here, the coupling of monolayers of perylene derivatives is investigated with bilayer MoS2. In particular, variation in the perylene orientation on the MoS2 surface is identified using Raman spectroscopy and scanning probe microscopy. Low‐temperature optical spectroscopy reveals orientation‐dependent interlayer exciton formation. Furthermore, power‐dependent photoluminescence measurements provide insight into the modified interlayer charge transfer in these heterostructures. A saturation of interlayer states is found under high excitation power when the perylene molecules are in a perpendicular orientation to the surface that leads to electron accumulation in the MoS2, whereas parallel alignment of the perylene molecules leads to enhanced populations of organic–inorganic interlayer excitons. This work provides insights into the optimization of organic–inorganic heterostructures, with particular relevance to applications for optoelectronic and excitonic devices.
The orientation of molecular layers in organic‐inorganic 2D heterostructures influences the optical properties of these hybrid systems. Interlayer excitons form between a self‐assembled monolayer of perylene and bilayer MoS2. The molecular alignment determines the charge transfer efficiency, resulting in high‐intensity interlayer excitons in the strong coupling regime, while their formation is limited in the weak coupling arrangement.