Efficient Near‐Infrared Light‐Emitting Diodes based on In(Zn)As–In(Zn)P–GaP–ZnS Quantum Dots

Abstract

Near‐infrared (NIR) lighting plays an increasingly important role in new facial recognition technologies and eye‐tracking devices, where covert and nonvisible illumination is needed. In particular, mobile or wearable gadgets that employ these technologies require electronic lighting components with ultrathin and flexible form factors that are currently unfulfilled by conventional GaAs‐based diodes. Colloidal quantum dots (QDs) and emerging perovskite light‐emitting diodes (LEDs) may fill this gap, but generally employ restricted heavy metals such as cadmium or lead. Here, a new NIR‐emitting diode based on heavy‐metal‐free In(Zn)As–In(Zn)P–GaP–ZnS quantum dots is reported. The quantum dots are prepared with a giant shell structure, enabled by a continuous injection synthesis approach, and display intense photoluminescence at 850 nm with a high quantum efficiency of 75%. A postsynthetic ligand exchange to a shorter‐chain 1‐mercapto‐6‐hexanol (MCH) affords the QDs with processability in polar solvents as well as an enhanced charge‐transport performance in electronic devices. Using solution‐processing methods, an ITO/ZnO/PEIE/QD/Poly‐TPD/MoO3/Al electroluminescent device is fabricated and a high external quantum efficiency of 4.6% and a maximum radiance of 8.2 W sr−1 m−2 are achieved. This represents a significant leap in performance for NIR devices employing a colloidal III–V semiconductor QD system, and may find significant applications in emerging consumer electronic products.

Deep Fluorescence Imaging by Laser‐Scanning Excitation and Artificial Neural Network Processing

“…The QD‐resin comprises a homogenous dispersion of QDs in isobornyl acrylate (IBOA) monomers and tricyclodecanedimethanol diacrylate (TCDDA) crosslinkers, and employs 2,2‐dimethoxy‐2‐phenylacetophenone (DMPA) as a radical photoinitiator. The In(Zn)As–In(Zn)P–GaP–ZnS‐based QDs were prepared according to our previous reports, [ 20,21 ] and emit at 837 nm (Figure S2, Supporting Information) with a high photoluminescence quantum yield of 75%. Figure a shows an image of the fluorescent panel under ambient lighting, taken using a Canon EOS M100 camera, and a fluorescence image, acquired using our laser‐scanning imaging setup.…”

High Quantum Yield Water‐Dispersed Near‐Infrared In(Zn)As–In(Zn)P–GaP–ZnS Quantum Dots with Robust Stability for Bioimaging

“…We first prepared the In(Zn)As–In(Zn)P–GaP–ZnS NIR QDs, stabilized by hydrophobic oleic acid (OA) ligands in hexane, using a convenient and scalable one‐pot continuous injection methodology which we have developed in earlier works (experimental details in the Supporting Information). [ 27–29 ] In brief, a small In(Zn)As core was first grown in a hot solution mixture containing indium oleate, zinc oleate, octylamine, and tris(trimethylsilyl)arsine ((TMS) 3 As) precursors. This is followed by the growth of a giant In(Zn)P shell through a slow, continuous injection of indium oleate, zinc oleate and tris(trimethylsilyl)phosphine ((TMS) 3 P) precursors.…”

“…[ 12,27 ] In order to harness the NIR PL emission tunability of InAs QDs, yet circumvent the use of toxic Cd‐based shells to obtain high PLQY, our group has recently developed quaternary giant‐shell InAs–In(Zn)P–ZnSe–ZnS and In(Zn)As–In(Zn)P–GaP–ZnS QDs using a continuous‐injection synthesis method, and demonstrated their application in NIR light‐emitting diodes. [ 28,29 ] Here, we present the preparation of water‐dispersed In(Zn)As–In(Zn)P–GaP–ZnS QDs that emit in the NIR at 828 nm with a best PLQY of 60%, and demonstrate their functional applications in the in vitro bioimaging of human cervical carcinoma HeLa cells. The use of a tiny In(Zn)As core resulted in a low As content (2%), which is further insulated from the external environment by three thicker shells, thus affording negligible cellular cytotoxicity even at a high QD concentration of 1 mg mL −1 .…”

When I Look into Your Eyes: A Survey on Computer Vision Contributions for Human Gaze Estimation and Tracking

“…It should be clarified that, in this work, the systems that use active illumination techniques will not be reviewed, unless they provide some innovation in terms of the computer vision technique, or in the case of more complete architectures where infrared only represents a fraction of the contribution. Indeed, this is a common and well-established technology, already on the market and with many patented approaches, although they still present their own specific challenges to be addressed and some research lines are still open, especially for improving electronic lighting components [ 26 ] Systems that use active illumination techniques have not received a dramatic improvement from the computer vision perspective, indeed, in our opinion, the summarization in [ 20 , 25 ] can be considered to be still valid. However, it is worth noting that this dyadic view (systems using active lighting vs systems not using active lighting) is relatively recent with respect to the time in which the early gaze tracking solutions appeared.…”