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The rapid development of optoelectronic devices with biomimetic synaptic behavior holds significant potential for neuromorphic visual applications. However, considerable challenges remain including convenient device fabrication and low toxicity materials innovation. Here, a heterojunction phototransistor is constructed using low‐toxic CuZnInSSe (CIZS) colloidal quantum dots and amorphous InGaZnO (IGZO), which demonstrates high specific detectivity of 3.4 × 1015 Jones in visible light spectrum. Moreover, it is found that the photoresponse speed can be controlled via a ligand exchange treatment, through that the response speed can be adjusted from 0.3 to 11 s. This enables the device to operate in two distinct modes: a typical fast sensing mode and a neuromorphic visual mode. In the neuromorphic visual mode, the device's synaptic behavior can be tuned by manipulating light pulse intensity, frequency, wavelength, and gate voltage. As a demonstration, a phototransistor array effectively implements image pre‐processing functions, including color recognition, visual memorizing, and forgetting. [ABSTRACT FROM AUTHOR]

Cadmium‐free quantum dot light‐emitting diodes (QLEDs) have held the potential to revolutionize the next‐generation displays with their advantages in color gamut, luminance intensity, and solution processibility. As a promising way of realizing large‐area QLED display production, inkjet printing has been intensively studied on Cd‐based QLEDs but lacks exploration in fabricating Cd‐free devices. Here, we developed Cd‐free RGB inkjet‐printed QLEDs with tailored hole transport layers (t‐HTLs) using Cd‐free QDs including InP/ZnSeS red and green QDs and ZnTeSe/ZnSe/ZnS blue QDs. With the t‐HTLs, QD ink erosion on the bottom charge transport layer was remarkably suppressed, while the efficient hole transport was maintained, which kept high device performance, especially in the QLED lifetime. With bank structures, Cd‐free QLED pixels were well defined within the size of 60 μm × 160 μm. Based on the t‐HTL structure and the bank structures, inkjet‐printed Cd‐free RGB QLED pixel arrays were demonstrated. This study bridges the gap between existing Cd‐free QLED technologies and the future commercialization of Cd‐free self‐emissive QD displays. [ABSTRACT FROM AUTHOR]

Blue indium phosphide quantum dot (InP QD) is an emerging colloidal semiconductor nanocrystal, considered as a promising next‐generation photoactive material for light‐emitting purposes. Despite the tremendous progress in blue InP QDs, the synthetic method for tailoring InP core size to realize the blue‐emissive QDs still lags behind. This work suggests a synthetic method for blue‐emitting InP QDs by engineering the core size with an incipient ZnS (i‐ZnS) shell. The formation of i‐ZnS complexes, before the tris(trimethylsilyl)phosphine injection (e.g., before core growth process), restrains the overgrowth of InP nuclei by rapidly forming a ZnS shell on its surface, thereby resulting in further dwarfed InP cores. With additional ZnS shell coating, the blue QDs exhibit a photoluminescence quantum yield of ≈52% at 483 nm. The origin of bandgap diminution with the increase of shell thickness, or with the utilization of ZnSe shell is unraveled via the first‐principles density functional theory simulations. Simulational evidence on InP‐core densification with the shell coating, along with accompanying changes in chemical and structural properties, is presented. The blue‐emitting InP QD device shows a maximum luminance of 1162 cd m−2 and external quantum efficiency of 1.4%. [ABSTRACT FROM AUTHOR]

The development of flexible displays for wearable electronics applications has created demand for high‐performance quantum dot (QD) light‐emitting diodes (QLEDs) based on QD core@shell structures. Emerging indium phosphide (InP)‐based core@shell QDs show promise as lighting material in the field of optoelectronics because they are environmentally friendly material, can be produced in a cost‐effective manner, and are capable of tunable emission. While efforts have been made to enhance the performance of InP‐based QLED, the stabilities of InP@ZnSeS QDs film and InP@ZnSeS‐based QLED in water/air are not yet fully understood, limiting their practical applications. Herein, a highly durable, flexible InP@ZnSeS QLED encapsulated in an ultrathin film of CYTOP, a solution‐based amorphous fluoropolymer, is demonstrated. The CYTOP‐encapsulated green flexible QLED shows an external quantum efficiency (EQE) of 0.904% and a high luminescence of 1593 cd m−2 as well as outstanding waterproof performance. The flexible device emits strong luminescence after being immersed in water for ≈20 min. Even when subjected to continuous tensile stress with a 5 mm bending radius, the high luminescence is preserved. This waterproof architecture can be a promising strategy for wearable electronics applications. [ABSTRACT FROM AUTHOR]