Enhanced Implied Open Circuit Voltage of MoS2 via Cation-based TFSI Passivation

Monolayer molybdenum disulphide (MoS2) holds great potential for optoelectronic and photovoltaic applications, yet its performance is limited by intrinsic defects, such as sulfur vacancies, that hinder photoluminescence (PL) and charge carrier dynamics. This study investigates the effects of passivation using cation-based bis(trifluoromethanesulfonimide) (TFSI) treatments (Li-TFSI, Cs-TFSI, and Rb-TFSI) on the optoelectronic properties of MoS2 monolayers. Implied open-circuit voltages (iV(oc)) at 1 sun illumination are taken from photoluminescence measurements, yielding post-treatment values of 1425, 1351, and 1381 mV for Li-TFSI, Rb-TFSI, and Cs-TFSI, respectively, indicating reduced non-radiative recombination. Optical absorption also increased after the cation-based TFSI treatment, leading to expected improvements in short-circuit current densities (J(SC)). These results demonstrate that cations can play an important role in reducing defect-related recombination and improving charge carrier dynamics, and that cation-based TFSI passivation may help to enhance the efficiency of MoS2-based optoelectronic devices.