Understanding the emergence of negative photoconductivity in CVD grown ReS ₂ thin films by invoking the trion generation mechanism

Emerging from robust coulombic interactions and diminished dielectric screening, two-dimensional transition metal dichalcogenides (2D TMDs) manifest strongly bound excitons. While these pronounced many-body effects have been observed in 2D TMDs, their impact on the materials' intrinsic photoconductive characteristics remains relatively less explored. In this study, a considerable reduction in photoconductivity in chemical vapor deposited (CVD) ReS₂ thin films has been observed. Through experimental and theoretical scrutiny, it is deduced that this anomalous phenomenon stems from the possible many-body interactions within the system, wherein photoexcited electron-hole pairs combine with excess electrons to generate trions. The formation of trions reduces the effective number of carriers contributing to photocurrent, thereby attenuating the photoconductivity. This study shows the profound influence of trions on the photoconductivity behaviour of ReS₂ thin films, thereby elucidating their significance in modulating optical and electrical properties crucial for optoelectronic applications.