Durable PDMS‐Interleaved WS ₂ Monolayer Composites for Enhanced Optical Absorbance and In‐Situ Strain Sensing

Abstract Oxidation causes WS 2 monolayers to lose optical and other functional properties during prolonged exposure to the atmosphere, limiting the practical applications. The degradation of WS 2 monolayers systematically over the period of four years is examined, and the distribution of degradation products in the monolayer flake is revealed by aberration‐corrected scanning transmission electron microscopy (STEM) and X‐ray photoelectron spectroscopy (XPS). To mitigate the degradation, a layered composite containing WS 2 monolayer and polydimethylsiloxane (PDMS) via controlled transfer and stacking is fabricated. The nanocomposite effectively preserved the WS 2 monolayer flakes unoxidized, retaining their optical properties even after one year. Furthermore, as the number of stacking layers increased, the strength of the A exciton peak increased by fourfold, leading to an enhancement in the absorbance of the WS 2 ‐PDMS composite. The developed layered composite enabled its use in flexible applications while maintaining its chemical stability and optical properties of WS 2 , even after 5000 fatigue cycles. Additionally, the in‐situ photoluminescence (PL) variation with strain is investigated, demonstrating the potential applicability of the composite for strain‐sensitive optical devices. A maximum strain transfer efficiency of 30% and an average gauge factor of 165 meV/strain are demonstrated to enable monolayer WS 2 ‐PDMS composite as a durable platform for flexible applications.