Optically coupled engineered upconversion nanoparticles and graphene for a high responsivity broadband photodetector

Area of Science:

• Materials Science
• Nanotechnology
• Optoelectronics

Background:

• Upconversion nanoparticle (UCNP)-graphene composites are emerging as promising photodetector materials.
• Optimizing optical coupling between UCNPs and graphene is crucial for device performance.

Purpose of the Study:

• To demonstrate a hybrid UCNP-graphene photodetector with enhanced sensitivity and gain.
• To investigate the effect of silica (SiO2) shell engineering on UCNP-graphene optical coupling and device parameters.

Main Methods:

• Fabrication of UCNP-graphene composites using core UCNPs and UCNP@SiO2 core-shell structures.
• Characterization of optical coupling via fluorescence enhancement and quenching.
• Performance evaluation of photodetectors under 980 nm excitation, measuring photoresponsivity, gain, and detectivity.

Main Results:

• Achieved significant enhancement in photodetector parameters through UCNP engineering.
• Demonstrated a photoresponsivity of ~2.7 × 10^4 A/W with UCNP@SiO2 devices, a substantial improvement over core-UCNP devices (~1.52 × 10^4 A/W).
• Obtained the highest reported responsivity, gain, and detectivity for this class of composite photodetectors.

Conclusions:

• Silica shell engineering of UCNPs effectively enhances optical coupling with graphene, leading to superior photodetector performance.
• The developed UCNP-graphene photodetectors exhibit high sensitivity and gain, enabling detection of signals from common handheld devices.
• This work advances the understanding of photophysics in UCNP-graphene hybrid systems for advanced optoelectronic applications.