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

Abstract

In this study we develop a strategy to insulate 6,6 -Phenyl C₆₁ butyric acid methyl ester (PCBM) on the basal plane of transition metal dichalcogenides (TMDs). Concretely single layers of MoS₂, MoSe₂, MoTe₂, WS₂, WSe₂ and WTe₂ and ultrathin MoO₂ and WO₂ 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-MoS₂, PCBM-MoSe₂, PCBM-WS₂, PCBM-WSe₂, PCBM-WTe₂, PCBM-MoO₂ and PCBM-WO₂. 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 MoS₂ devices, the conductivity and photoluminescence (PL) emission achieve a remarkable enhancement of 1700 % and 200 % in PCBM-MoS₂ hybrids. Similarly, PCBM-MoTe₂ hybrids exhibit a 2-fold enhancement in PL emission at 1.1 eV. On the other hand, PCBM-MoSe₂, PCBM-WSe₂ and PCBM-WS₂ 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-WTe₂ and PCBM-WO₂ showed a modest photo-response, in sharp contrast with pristine WTe₂ or WO₂ which archive pure metallic character.

Keywords: PCBM; TMDs; covalent functionalization; energy conversion; nanomaterials.