skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


  • NSF Public Access
  • Search Results
  • High resolution patterning of PbS quantum dots/graphene photodetectors with high responsivity via photolithography with a top graphene layer to protect surface ligands
Title: High resolution patterning of PbS quantum dots/graphene photodetectors with high responsivity via photolithography with a top graphene layer to protect surface ligands
Photodetectors based on colloidal quantum dots (CQDs) and single layer graphene (SLG) have shown high responsivity due to the synergy of strong light absorption from CQDs and high mobility from SLG. However, it is still challenging to achieve high-density and small-footprint devices on a chip to meet the demand for their integration into electronic devices. Even though there are numerous approaches to pattern the chemically fragile CQD films, usually they require non-conventional approaches such as stamping and surface modification that may be non-compatible with semiconductor processing. In this study, we show that conventional lithography and dry etching can be used to pattern QD active films by employing a graphene monolayer passivation/protective layer that protects the surface ligands of CQDs. This protective layer avoids damage induced by lithography process solvents that deteriorate the carrier mobility of CQDs and therefore the photoresponse. Herein we report patterning of CQDs using conventional UV photolithography, achieving reproducible five-micron length PbS CQDs/SLG photodetectors with a responsivity of 10 8 A W −1 . We have also fabricated thirty-six PbS CQDs/SLG photodetectors on a single chip to establish micron size photodetectors. This process offers an approach to pattern QDs with conventional UV lithography and dry etching semiconductor technology to facilitate their integration into current semiconductor commercial technology.  more » « less
Award ID(s):
2046176
PAR ID:
10335076
Author(s) / Creator(s):
; ;
Date Published:
Journal Name:
Nanoscale Advances
Volume:
3
Issue:
21
ISSN:
2516-0230
Page Range / eLocation ID:
6206 to 6212
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; ; ; ; et al (, Molecules)
    Optoelectronic devices combining single-layer graphene (SLG) and colloidal semiconducting nanocrystal (NC) heterojunctions have recently gained significant attention as efficient hybrid photodetectors. While most research has concentrated on systems using heavy metal-based semiconductor NCs, there is a need for further exploration of environmentally friendly nanomaterials, such as Cu2−xS. Chemical ligands play a crucial role in these hybrid photodetectors, as they enable charge transfer between the NCs and SLG. This study investigates the photoresponse of an SLG/Cu2−xS NCs heterojunction, comparing the effect of two short molecules—tetrabutylammonium iodide (TBAI) and 3,4-dimethylbenzenethiol (DMBT)—as surface ligands on the resulting structures. We have analysed charge transfer at the heterojunctions between SLG and the Cu2−xS NCs before and after modification with TBAI and DMBT using Raman spectroscopy and transconductance measurements under thermal equilibrium. The photoresponse of two hybrid devices based on three layers of Cu2₋xS NCs, deposited in one case on SLG/Cu2−xS/TBAI (“TBAI-only” device) and in the other on SLG/Cu2−xS/DMBT (“DMBT + TBAI” device), with a TBAI treatment applied, for both, after each layer deposition, has been evaluated under 450 nm laser diode illumination. The results indicate that the TBAI-only device exhibited a significant increase in photocurrent (4 μA), with high responsivity (40 mA/W) and fast response times (<1 s), while the DMBT + TBAI device had lower photocurrent (0.2 μA) and responsivity (2.4 μA), despite similar response speeds. The difference is attributed to DMBT’s π–π interactions with SLG, which enhances electronic coupling but reduces SLG’s mobility and responsivity. 
    more » « less
  2. ; ; ; ; ; ; ; ; (, Advanced Electronic Materials)
    Abstract Hybrid graphene and quantum dots (QDs) photodetectors merge the excellent conductivity and ambipolar electric field sensitivity of graphene, with the unique properties of QDs. The photoresponsivity of these devices depends strongly on the charge transfer at the graphene/QDs interface. Here 1‐pyrene butyric acid (PBA)‐coated PbS QDs with single layer graphene (SLG) are used to investigate the effect of pyrene as a π–π mediator to enhance charge transfer at the SLG/QDs junction under illumination. The surface chemistry at the QD–QD and SLG/QD interface is studied with the conventional tetrabutylammonium iodide (TBAI) QD linker. The hybrid SLG/QD photodetectors with PBA as a SLG‐QD linker demonstrate a photoresponse up to 30% higher than that recorded for devices where only TBAI is used, due to the strong electron coupling between SLG and QDs. Transconductance measurements show that PBA provokes electron depletion in SLG ascribed to the tendency to delocalize the QDs holes, favoring their transfer to SLG. This surface ligand is found to improve the interaction between the QDs light absorbers and the SLG charge collector, leading to an increased photodetection response. This demonstrates that ligand engineering can enhance charge dynamics and boost the performance of the hybrid device. 
    more » « less
  3. ; ; ; ; ; (, Advanced Electronic Materials)
    Abstract Hybrid graphene (Gr)–quantum dot (QD) photodetectors have shown ultrahigh photoresponsivity combining the strong light absorption of QDs with the high mobility of Gr. QDs absorb light and generate photocarriers that are efficiently transported by Gr. Typically, hybrid PbS–QD/graphene photodetectors operate by transferring photogenerated holes from the QDs to Gr while photoelectrons stay in the QDs inducing a photogating mechanism that achieves a responsivity of 6 × 107A W−1. However, despite such high gain, these systems have poor charge collection with quantum efficiency below 25%. Herein, a ZnO intermediate layer (PbS‐QD/ZnO/Gr) is introduced to improve charge collection by forming an effective p‐n PbS‐ZnO junction driving the electrons to the ZnO layer and then to Gr. This improves the photoresponsivity of the devices by nearly an order of magnitude with respect to devices without ZnO. Charge transfer to Gr is demonstrated by monitoring the change in Fermi level under illumination for conventional PbS‐QD/Gr and for ZnO intermediate PbS‐QD/ZnO/Gr devices. These results improve the capabilities of hybrid QD/Gr configurations for optoelectronic devices. 
    more » « less
  4. ; ; ; (, Infrared Technology and Applications XLVII, Vol 117410F (2021) SPIE Defense + Commercial Sensing (2021))
    Fulop, Gabor F.; Kimata, Masafumi; Zheng, Lucy; Andresen, Bjørn F.; Miller, John Lester (Ed.)
    Colloidal semiconductor quantum dots/graphene van der Waals (vdW) heterojunctions take advantages of the enhanced light-matter interaction and spectral tenability of quantum dots (QDs) and superior charge mobility in graphene, providing a promising alternative for uncooled infrared photodetectors with a gain or external quantum efficiency up to 1010. In these QD/graphene vdW heterostructures, the QD/graphene interface plays a critical role in controlling the optoelectronic process including exciton dissociation, charge injection and transport. Specifically, charge traps at the vdW interface can increase the noise, reduce the responsivity and response speed. This paper highlight our recent progress in engineering the vdW heterojunction interface towards more efficient charge transfer for higher photoresponsivity, D* and response speed. These results illustrate that the importance in vdW heterojunction interface engineering in QD/graphene photodetectors which may provide a promising pathway for low-cost, printable and flexible infrared detectors and imaging systems. 
    more » « less
  5. ; ; ; ; ; ; ; ; (, Advanced Materials Interfaces)
    Abstract Graphene, a single layer conductor, can be combined with other functional materials for building efficient optoelectronic devices. However, transferring large‐area graphene onto another material often involves dipping the material into water and other solvents. This process is incompatible with water‐sensitive materials such as organometal halide perovskites. Here, a dry method is used and succeeded, for the first time, in stacking centimeter‐sized graphene directly onto methylammonium lead iodide thin films without exposing the perovskite film to any liquid. Photoemission spectroscopy and nanosecond time‐resolved photoelectrical measurement show that the graphene/perovskite interface does not contain significant amount of contaminants and sustain efficient interfacial electron transfer. The use of this method in fabricating graphene‐on‐perovskite photodetectors is further demonstrated. Besides a better photoresponsivity compared to detectors fabricated by the conventional perovskite‐on‐graphene structure, this dry transfer method provides a scalable pathway to incorporate graphene in multilayer devices based on water‐sensitive materials. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email