All-Printable ZnO Quantum Dots/Graphene van der Waals Heterostructures for Ultrasensitive Detection of Ultraviolet Light

Abstract

In ZnO quantum dot/graphene heterojunction photodetectors, fabricated by printing quantum dots (QDs) directly on the graphene field-effect transistor (GFET) channel, the combination of the strong quantum confinement in ZnO QDs and the high charge mobility in graphene allows extraordinary quantum efficiency (or photoconductive gain) in visible-blind ultraviolet (UV) detection. Key to the high performance is a clean van der Waals interface to facilitate an efficient charge transfer from ZnO QDs to graphene upon UV illumination. Here, we report a robust ZnO QD surface activation process and demonstrate that a transition from zero to extraordinarily high photoresponsivity of 9.9 × 10 A/W and a photoconductive gain of 3.6 × 10 can be obtained in ZnO QDs/GFET heterojunction photodetectors, as the ZnO QDs surface is systematically engineered using this process. The high figure-of-merit UV detectivity D* in exceeding 1 × 10 Jones represents more than 1 order of magnitude improvement over the best reported previously on ZnO nanostructure-based UV detectors. This result not only sheds light on the critical role of the van der Waals interface in affecting the optoelectronic process in ZnO QDs/GFET heterojunction photodetectors but also demonstrates the viability of printing quantum devices of high performance and low cost.

Disclosing Interfaces of ZnO Nanocrystals Using Dynamic Nuclear Polarization: Sol‐Gel versus Organometallic Approach

“…It could also be related to an inherently highly‐defected and corrugated surface structure and an unstable resulting nanocrystal‐ligand interface (e.g., Gong et al. demonstrated that sol‐gel derived ZnO NCs with a stable surface structure could be achieved after a one‐month aging process). Wet‐organometallic approaches are highly promising alternatives to the omnipresent sol‐gel method .…”

2D In2S3 Nanoflake Coupled with Graphene toward High‐Sensitivity and Fast‐Response Bulk‐Silicon Schottky Photodetector

“…Figure c depicts the measured photocurrent of the In 2 S 3 /graphene/Si PD as a function of 405 nm light intensity at a fixed V ds = −2 V. The photocurrent can be expressed by a simple power law I ph ∝ P 0.18 for weak light and I ph ∝ P 0.02 for strong light. Here, the nonunity of exponent can be associated with the complex process of electron–hole excitation, trapping, and recombination within the In 2 S 3 /graphene/Si heterojunction …”

Recent Progress of Heterojunction Ultraviolet Photodetectors: Materials, Integrations, and Applications

“…c) 2D‐0D Hybrid vdWs heterostructure device based on ZnO QD/graphene and its selective UV response according to the spectral performance. Reproduced with permission 146. Copyright 2017, American Chemical Society.…”

“…The hybrid vdWs heterostructures combine UV photosensitivity and high carrier mobility, and a promoted UV detection (usually broadband spectral response) is achieved. For example, ZnO QDs are printed on graphene and generated a 2D‐0D hybrid vdWs heterostructure with ultrasensitive detection of UV light,146 and other nanocrystals like FeS 2 ‐PbS149 and FeS 2 150 are utilized to similarly strengthen the light absorption in other reports. Apart from the 2D‐0D hybrid vdWs structures, 2D‐0D hybrid structures based on bulk semiconductor crystals are also reported.…”