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1. High resolution patterning of PbS quantum dots/graphene photodetectors with high responsivity via photolithography with a top graphene layer to protect surface ligands

   https://doi.org/10.1039/d1na00582k  

   Ahn, Seungbae; Chen, Wenjun; Vazquez-Mena, Oscar (October 2021, Nanoscale Advances)

   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. 

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2. PbS colloidal quantum dot photovoltaics: progress towards infrared and flexible applications

   https://doi.org/10.1039/d5cc03198b  

   Chintapalli, Sreyas M; Li, Lulin; Thon, Susanna M (January 2025, Chemical Communications)

   PbS colloidal quantum dots (CQDs) are a promising material class for near-infrared optoelectronics. 

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3. Coupling of Infrared Active Colloidal Quantum Dots and Amorphous Selenium for Fast and Sensitive Photodetection

   https://doi.org/10.1002/adfm.202315304  

   Mølnås, Håvard; Mukherjee, Atreyo; Kannan, Haripriya; Han, Zhihang; Ravi, Vikash_K; Paul, Shlok_J; Rumaiz, Abdul_K; Zhao, Wei; Goldan, Amir_H; Sahu, Ayaskanta (May 2024, Advanced Functional Materials)

   Abstract Colloidal quantum dot (CQD) based infrared (IR) photodetectors offer facile wavelength tunability in the IR and low‐cost fabrication. However, owing to their large surface areas, CQDs intrinsically have significant surface traps critically affecting the speed of CQD photodetectors, typically mediated through tedious surface passivation efforts. In this report, an alternative strategy involving coupling of near‐IR photoactive lead sulfide CQDs with a thermally evaporated amorphous selenium (a‐Se) hole transport layer is proposed. By separating the detector into a photon absorbing CQD region and a charge transport a‐Se region, the study takes advantage of the extremely low noise, predominantly hole‐only transport process in a‐Se. A high 3 dB bandwidth of 2.5 MHz and a competitive specific detectivity of 2.5 × 10¹¹Jones at room temperature are demonstrated at 980 nm. This report serves as a first demonstration of strong coupling between an IR active CQD absorber and a‐Se, which paves the path to obtain fast and highly photoresponsive IR photodetection in the future. 

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4. Carbon Quantum Dot Modified Reduced Graphene Oxide Framework for Improved Alkali Metal Ion Storage Performance

   https://doi.org/10.1002/smll.202202898  

   Jin, Shikai; Allam, Omar; Lee, Kyungbin; Lim, Jeonghoon; Lee, Michael J.; Loh, Sze Hou; Jang, Seung Soon; Lee, Seung Woo (August 2022, Small)

   Abstract Organic materials with redox‐active oxygen functional groups are of great interest as electrode materials for alkali‐ion storage due to their earth‐abundant constituents, structural tunability, and enhanced energy storage properties. Herein, a hybrid carbon framework consisting of reduced graphene oxide and oxygen functionalized carbon quantum dots (CQDs) is developed via the one‐pot solvothermal reduction method, and a systematic study is undertaken to investigate its redox mechanism and electrochemical properties with Li‐, Na‐, and K‐ions. Due to the incorporation of CQDs, the hybrid cathode delivers consistent improvements in charge storage performance for the alkali‐ions and impressive reversible capacity (257 mAh g⁻¹at 50 mA g⁻¹), rate capability (111 mAh g⁻¹at 1 A g⁻¹), and cycling stability (79% retention after 10 000 cycles) with Li‐ion. Furthermore, density functional theory calculations uncover the CQD structure‐electrochemical reactivity trends for different alkali‐ion. The results provide important insights into adopting CQD species for optimal alkali‐ion storage. 

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5. New Chalcogenide-Based Hole Transport Materials for Colloidal Quantum Dot Photovoltaics

   Rong, Eric; Bambini, Christianna; Lin, Yida; Lu, Chengchangfeng; Thon, Susanna M. (January 2021, Conference record of the IEEE Photovoltaic Specialists Conference)

   null (Ed.)

   Colloidal Quantum Dot (CQD) thin films are ad- vantageous for solar energy generation because of their low- cost and size-tunable, solution-processable nature. However, their efficiency in solar cells is limited in part by the performance of the hole transport layer (HTL). Through Solar Cell Capacitance Simulations and Transfer Matrix Method calculations, we show that significant photogeneration occurs in the standard HTL of ethanedithiol-passivated lead sulfide CQDs which is a problem due to the sub-optimal carrier mobility in this material. We report new HTLs composed of chalcogenide-based materials to address these issues, and demonstrate an absolute power conversion efficiency improvement of 1.35% in the best device. 

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