Interfacial Band Engineering in ZnO-Carbon Quantum Dot Hybrids for Next-Generation Ultraviolet Photodetectors

Area of Science:

• Materials Science
• Nanotechnology
• Optoelectronics

Background:

• Planar zinc oxide (ZnO) ultraviolet (UV) photodetectors offer low-power optoelectronic solutions but face challenges with limited responsivity due to surface recombination and inefficient carrier separation.
• Vertically aligned nanostructures can improve charge transport and light absorption compared to thin films.

Purpose of the Study:

• To develop a high-performance UV photodetector using vertically aligned ZnO nanorods (ZNRs) hybridized with nitrogen-doped carbon quantum dots (NCQDs).
• To investigate the impact of NCQD coating and ZNR architecture on photodetector performance, including photocurrent density, responsivity, and external quantum efficiency (EQE).

Main Methods:

• Fabrication of vertically aligned ZnO nanorods (ZNRs).
• Coating ZNRs with nitrogen-doped carbon quantum dots (NCQDs).
• Characterization of photodetector performance, including photocurrent density, responsivity, and EQE under UV illumination.

Main Results:

• The ZNR device showed improved photocurrent density (~10⁻⁴ Acm⁻²) and EQE (~75%) compared to planar ZnO thin film (ZTF) devices.
• The NCQD-coated ZNR device exhibited a significant enhancement, with photocurrent density reaching 10⁻² Acm⁻², responsivity >2 AW⁻¹, and EQE approaching 730%.
• Enhanced performance is attributed to stepwise band alignment promoting electron accumulation, NCQD surface passivation, and interfacial carrier trapping.

Conclusions:

• Vertically oriented architecture and interfacial band engineering are crucial for high-gain ZnO-based UV photodetectors.
• NCQD hybridization offers a scalable strategy to significantly boost UV detection capabilities.
• This approach paves the way for advanced, low-power optoelectronic platforms.