Synthesis and photoelectric properties of TlInS2 nanoflake-doped PVP thin-film photodetectors

This study investigates the electrical transport and optoelectronic properties of polymer-based nanocomposite thin films, specifically pristine polyvinylpyrrolidone (PVP) and PVP:TlInS₂ composites, fabricated as photodetectors on n-Si substrates. Current–voltage (I–V) measurements revealed rectifying behavior characteristic of Schottky-like junctions, with current transport primarily governed by thermionic emission, albeit influenced by non-ideal factors, such as interface states and series resistance. The incorporation of TlInS₂ significantly enhanced the electrical conductivity of the composite film by orders of magnitude compared to pristine PVP, attributed to improved charge transport pathways. Illumination-dependent I–V characteristics demonstrated an apparent increase in photocurrent with increasing light intensity for both devices. Quantitative analysis of optoelectronic parameters showed that the PVP:TlInS₂ composite exhibited superior responsivity (up to 0.513 A/W) and achieved an external quantum efficiency exceeding 100% (up to 117.1%), indicating photoconductive gain. Crucially, the composite device demonstrated a remarkably low noise equivalent power (10⁻¹⁴ W/Hz^1/2) and a high detectivity (> 10¹³ cm Hz^1/2/W), representing a two order-of-magnitude improvement over the pristine PVP. This enhanced sensitivity is primarily due to the substantial reduction in dark current. Furthermore, time-dependent photocurrent measurements confirmed the device’s stable, fast, and repeatable “On–Off” switching capabilities. These findings highlight the potential of PVP:TlInS₂ nanocomposites for developing high-performance, sensitive, and efficient optoelectronic devices.