Opto-electronic Properties of Hybrid C8-BTBT/Monolayer Transition Metal Dichalcogenide Heterostructures

C8-BTBT (2,7-dioctyl[1]benzothiophene[2,3-b]benzothiophene) is a wide bandgap organic semiconductor. When it is interfacing with transition metal dichalcogenides (TMD) such as monolayer WS₂ and MoS₂, they form a type-I heterostructure. The near electrostatic field from the C8-BTBT can modify the optoelectronic property of the TMD layer. To form the hybrid type-I heterostructure, we deposited a thin layer of C8-BTBT on monolayer MoS₂. We determined band alignment of the heterostructure using ultraviolet photoelectron spectroscopy (UPS). Moreover, time- and frequency- resolved photoluminescence (Tr-PL) spectroscopy was used to study the exciton dynamics. We observe the quenching of the WS₂’s PL signal after the C8-BTBT deposition. This observation can indicate that electrons and holes within the WS₂ are separated from each other because of the electrostatic potential imposed by the C8-BTBT layer.  This modification significantly increases the exciton lifetime in the WS₂ layer.