Enhanced Photoluminescence in Encapsulated TFSI treated MoS₂

Semiconducting transition metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS₂) are 2D materials that possess a direct bandgap at a single-layer thickness. Their bandgap makes them ideal for optical sensing and switching applications. However, the function of as-fabricated MoS2 optoelectronic devices is throttled by their extremely low photoluminescence quantum yield (PLQY) of 0.01%-0.6% [1]. Surprisingly, recent literature has demonstrated methods to drastically increase PLQY using chemical treatments and electrostatic doping [1]. Here we demonstrate significantly enhanced photoluminescence (PL) up to an order of magnitude in MoS₂ using trifluoromethansulfonimide (TFSI) acid treatment. We observe a suppression of a charged exciton feature suggesting a reduction in non-radiative recombination via charge-neutralization. Additionally, as the PL enhancing effects of TFSI-acid deteriorate after exposure to standard lithography solutions, we attempt to remedy this using hexagonal boron nitride (hBN) encapsulation. While TFSI-acid treated MoS₂ demonstrates increased PL efficiency, hBN encapsulation is mixed for protecting the enhanced PLQY.

[1] D. Lien, S. Z. Uddin, M. Yeh, M. Amani, H. Kim, J. W. Ager, E. Yablonovitch, and A. Javey,
Science, 364 (2019) 468-471.