Insulating 6,6-Phenyl-C61-butyric Acid Methyl Ester on Transition-Metal Dichalcogenides: Impact of the Hybrid Materials on the Optical and Electrical Properties.

In this study we develop a strategy to insulate 6,6 -Phenyl C butyric acid methyl ester (PCBM) on the basal plane of transition metal dichalcogenides (TMDs). Concretely single layers of MoS, MoSe, MoTe, WS, WSe and WTe and ultrathin MoO and WO were grown via chemical vapor deposition (CVD). Then, the thiol group of a PCBM modified with cysteine reacts with the chalcogen vacancies on the basal plane of TMDs, yielding PCBM-MoS, PCBM-MoSe, PCBM-WS, PCBM-WSe, PCBM-WTe, PCBM-MoO and PCBM-WO. Afterwards, all the hybrid materials were characterized using several techniques, including XPS, Raman spectroscopy, TEM, AFM, and cyclic voltammetry. Furthermore, PCBM causes a unique optical and electrical impact in every TMDs. For MoS devices, the conductivity and photoluminescence (PL) emission achieve a remarkable enhancement of 1700 % and 200 % in PCBM-MoS hybrids. Similarly, PCBM-MoTe hybrids exhibit a 2-fold enhancement in PL emission at 1.1 eV. On the other hand, PCBM-MoSe, PCBM-WSe and PCBM-WS hybrids exhibited a new interlayer exciton at 1.29-1.44, 1.7 and 1.37-154 eV along with an enhancement of the photo-response by 2400, 3200 and 600 %, respectively. Additionally, PCBM-WTe and PCBM-WO showed a modest photo-response, in sharp contrast with pristine WTe or WO which archive pure metallic character.