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Viologen-based electrochromic (EC) materials have been widely applied in smart mirrors and glasses for decades owing to their excellent properties, including outstanding reversibility, abundant color-regulation, and fast response. However, for a viologen-based EC device, inadequate ideal coloring uniformity and dissolution stability exist as limitations. Herein, a novel cardo fluorene-grafted viologen derivative (FPV) was designed and synthesized. Benefiting from the conjugated and twisted structure of fluorene-based cardo, the EC device based on FPV exhibited a promising EC property with a uniform coloring process and long-term dissolution stability. Considering these beneficial properties, the application of this device in a smart window (>25 cm2) was successfully demonstrated. This unique exploration exhibited a creative and high-efficiency route to solve the existing problems of coloring uniformity and dissolution stability in viologen-based EC devices, which can undoubtedly facilitate the development and commercial application of viologen-based EC materials. [ABSTRACT FROM AUTHOR]

A stimuli‐responsive multiple chirality switching material, which can regulate opposed chiral absorption characteristics, has great application value in the fields of optical modulation, information storage and encryption, etc. However, due to the rareness of effective functional systems and the complexity of material structures, developing this type of material remains an insurmountable challenge. Herein, a smart polymer film with multiple chirality inversion properties was fabricated efficiently based on a newly‐designed acid & base‐sensitive dye‐grafted helical polymer. Benefited from the cooperative effects of various weak interactions (hydrogen bonds, electrostatic interaction, etc.) under the aggregated state, this polymer film exhibited a promising acid & base‐driven multiple chirality inversion property containing record switchable chiral states (up to five while the solution showed three‐state switching) and good reversibility. The creative exploration of such a multiple chirality switching material can not only promote the application progress of current chiroptical regulation technology, but also provide a significant guidance for the design and synthesis of future smart chiroptical switching materials and devices. [ABSTRACT FROM AUTHOR]

Quasi‐2D perovskites light‐emitting diodes (PeLEDs) have achieved significant progress due to their superior optical and electronic properties. However, the blue PeLEDs still exist inefficient energy transfer and electroluminescence performance caused by mixed multidimensional phase distribution. In this work, transition metal salt (zinc bromide, ZnBr2) is introduced to modulate phase distributions by suppressing the nucleation of high n phase perovskites, which effectively shortens the energy transfer path for blue emission. Moreover, ZnBr2 also facilitates energy level matching and reduces non‐radiative recombination, thus improving electroluminescence (EL) efficiency. Benefiting from these combined improvements, an efficient blue PeLEDs is obtained with a maximum external quantum efficiency (EQE) of 16.2% peaking located at 486 nm. This work provides a promising approach to tune phase distribution of quasi‐2D perovskites and achieving highly efficient blue PeLEDs. [ABSTRACT FROM AUTHOR]

Compared to conventional quantum dot light-emitting diodes (QLEDs), tandem QLEDs (TQLEDs) have the advantages of long lifetime, high brightness and high efficiency, thereby making them potential candidates for display and lighting applications. In this work, ZnMgO/PEDOT:PSS was employed as the interconnecting layer (ICL) to fabricate TQLEDs, achieving brightness doubling at the equivalent current. Further, the devices exhibited a maximum external quantum efficiency (EQE) of 35.51%, which is currently the largest EQE reported for the full-solution process of manufacturing red TQLEDs. The improvement in TQLED efficiency can be attributed to the optimization of the electronic transport layer (ETL), which is achieved by adjusting the Mg doping level in ZnO. This process facilitated a balanced electron and hole injection and limited the photoluminescence (PL) quenching of QDs by ZnO. Furthermore, it can also be attributed to the effective charge generation capacity of ZnMgO/PEDOT:PSS along with the resistance of ZnMgO to acids. [ABSTRACT FROM AUTHOR]

Even though lead halide perovskite has been demonstrated as a promising optoelectronic material for next-generation display applications, achieving high-efficiency and stable pure-red (620~635 nm) emission to cover the full visible wavelength is still challenging. Here, we report perovskite light-emitting diodes emitting pure-red light at 628 nm achieving high external quantum efficiencies of 26.04%. The performance is attributed to successful synthesizing strongly confined CsPbI3 quantum dots with good stability. The strong binding 2-naphthalene sulfonic acid ligands are introduced after nucleation to suppress Ostwald ripening, meanwhile, ammonium hexafluorophosphate exchanges long chain ligands and avoids regrowth by strong binding during the purification process. Both ligands enhance the charge transport ability of CsPbI3 quantum dots. The state-of-the-art synthesis of pure red CsPbI3 quantum dots achieves 94% high quantum efficiency, which can maintain over 80% after 50 days, providing a method for synthesizing stable strong confined perovskite quantum dots. Li et al. report the regulation of perovskite quantum dot growth after nucleation by designing ligand exchange utilising proton transfer. The Ostwald ripening and regrowth are prohibited with an external quantum efficiency of 26.04% achieved in the pure-red perovskite light-emitting diodes. [ABSTRACT FROM AUTHOR]

The n‐type quantum dot (QD) active layer is the core component of lead sulfide QD solar cells (PbS QDSCs). In the state‐of‐the‐art PbS QDSCs, the active layer is commonly obtained through liquid‐phase ligand exchange (LPLE). Due to the intricate chemical state of the ligand exchange solution providing halide ligand, therefore, the PbS‐OAQD solutions is used at concentrations of 20, 30, and 40 mg mL−1 for LPLE, aiming to investigate the reasons for different surface states post‐exchange and their impact on device performance. The results indicate that when the concentration of the PbS‐OA QD solution is 30 mg mL−1, the exchanged QDs exhibit complete removal of surface OA, a higher content of short‐chain ligand PbX2 (X = I, Br), Consequently, devices fabricated using PbS‐PbX2 QD obtained through the exchange of 30 mg mL−1 PbS‐OA QD solution achieve a higher power conversion efficiency (PCE) of 12.53%. This study presents a simple and effective strategy to enhance the performance of PbS QDSCs. [ABSTRACT FROM AUTHOR]

Inorganic perovskite quantum dots (QDs) have garnered significant attention due to their outstanding optical properties. However, perovskite quantum dot light‐emitting diodes (Pe‐QLEDs) still face challenges related to their fluorescence efficiency and electron injection. First, the electron transport layer (ETL) leads to severe non‐radiative recombination due to fluorescence quenching in CsPbI3 QDs. Second, there is an electron injection imbalance resulting from low electron injection efficiency, leading to reduced non‐radiative recombination and external quantum efficiency. To address these issues, this study introduces two interface layer materials with different electron affinities, 1,3,5‐Tris(3‐pyridyl‐3‐phenyl)benzene (TmPyPB) and 2,4,6‐Tris(3′‐(pyridine‐3‐yl)biphenyl‐3‐yl)‐1,3,5‐triazine (TmPPPyTz). These materials not only passivated defects on the surface of CsPbI3 QDs films but also effectively prevented the fluorescence quenching of CsPbI3 QDs by the PO‐T2T (ETL). TmPPPyTz, with a relatively lower LUMO energy level, further improved energy level matching, significantly enhancing electron injection efficiency. Ultimately, using interface engineering with the TmPPPyTz interface layer, the devices achieved an outstanding 25.80% champion‐level external quantum efficiency (EQE) for Pe‐QLEDs with only a sub‐bandgap voltage of 1.7 V and half‐life (T50) is 17.99 h at 100 nits. This research provided an effective method to enhance the performance of CsPbI3 Pe‐QLEDs, addressing long‐standing issues inhibiting their efficiency. [ABSTRACT FROM AUTHOR]

Poly(3,4-ethylene dioxythiophene)/poly(styrene sulfonic acid), abbreviated as PEDOT:PSS, is widely used in light-emitting diodes, solar cells, sensors, and other functional devices due to its high conductivity, transparency, and solution processability. In this study, the photo-reactive cross-linking agent 2,4-hexadiyne-1,6-diol (HOD) was introduced for a comparative study of photo-crosslinking in PEDOT:PSS AI 4083 (denoted as 4083) and PEDOT:PSS PH1000 (denoted as PH1000). The results showed that the aggregation state of 4083 was different from that of PH1000, ascribed to the composition of 4083 and PH1000 and the mechanism of the photo-crosslinking agent. Based on these findings, quantum dot light-emitting diode (QLED) devices were fabricated using direct photo-crosslinking PH1000. The work function based on PH1000 as a hole-injected layer (HIL) was increased from 5.03 eV to 5.22 eV, and the external quantum efficiency (EQE) was increased from 17.2% to 18.9%. This result provided a feasible solution for the application of PH1000 in high-performance QLED displays. [ABSTRACT FROM AUTHOR]

Quantum dot light-emitting diodes (QLEDs) are emerging as promising contenders for next-generation display technology owing to their remarkable performance. In extensive research on QLEDs, MoO3 is commonly used as a replacement for the acidic hole injection material PEDOT:PSS to avoid acid corrosion of the indium tin oxide (ITO) electrode, thus preventing degradation of QLED performance. The advantages of solution-processed QLEDs make them an attractive option for large-scale production. Nowadays, achieving pixelation is still a critical step in the commercialization of QLEDs. In this work, we synthesized ultrafine MoO3 nanoparticles with an average grain size around 2 nm and successfully achieved MoO3 patterns through direct photolithography by incorporating photosensitizers. Furthermore, QLED devices with the photolithographed MoO3 as the hole injection layer (HIL) were fabricated, and pixel patterns with different shapes were designed and achieved. Compared to QLEDs based on pristine MoO3, the devices with photolithographic MoO3 exhibited a higher external quantum efficiency (EQE) and brightness. We believed that this work could establish a technological foundation for the development of high-resolution QLED displays. [ABSTRACT FROM AUTHOR]

Lead sulfide (PbS) colloidal quantum dot (CQD) materials are extensively utilized in the fabrication of near-infrared detectors. Advanced PbS quantum dot infrared detectors often employ ligand exchange processes to enhance the performance of the active layer. This process involves the replacement of long-chain ligands, which exhibit poor conductivity, with short-chain ligands, such as 1,2-ethanedithiol (EDT) in the treatment of PbS. However, conventional solid-state ligand exchange techniques are prone to cause inherent cracking, resulting in significant leakage currents that limit detector sensitivity. To address this challenge, we introduce a copper indium selenium sulfur (CuInSeS) quantum dot interfacial layer, resulting in the creation of a smooth and crack-free film. This method effectively optimizes the interfacial contact between PbS and ZnO. Additionally, this layer concurrently establishes a gradient energy level, facilitating the transport of charge carriers. This results in a decrease in the dark current to 4.6 × 10−8 mA under a −1 V bias, achieving a detectivity of 1.87 × 1012 Jones. The results demonstrate that the quantum dot interfacial layer effectively suppresses the dark current of the detector, addressing the deficiencies associated with the solid-state ligand exchange technique. This work provides a direction for further research on detectors. [ABSTRACT FROM AUTHOR]

Highlights: A new proton-promoted in situ ligand exchange strategy based on CsPbI3 quantum dots. The ligand exchange strategy maintains the quantum confinement effect of quantum dots and significantly improves the stability and photophysical properties of CsPbI3 quantum dots. The performance of light-emitting diodes based on CsPbI3 quantum dots is significantly improved, the external quantum efficiency is increased from 18.63% to 24.45%, and the half-operational lifetime is increased by 70 times. CsPbI3 perovskite quantum dots (QDs) are ideal materials for the next generation of red light-emitting diodes. However, the low phase stability of CsPbI3 QDs and long-chain insulating capping ligands hinder the improvement of device performance. Traditional in-situ ligand replacement and ligand exchange after synthesis were often difficult to control. Here, we proposed a new ligand exchange strategy using a proton-prompted in-situ exchange of short 5-aminopentanoic acid ligands with long-chain oleic acid and oleylamine ligands to obtain stable small-size CsPbI3 QDs. This exchange strategy maintained the size and morphology of CsPbI3 QDs and improved the optical properties and the conductivity of CsPbI3 QDs films. As a result, high-efficiency red QD-based light-emitting diodes with an emission wavelength of 645 nm demonstrated a record maximum external quantum efficiency of 24.45% and an operational half-life of 10.79 h. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) have attracted wide attention from academia and industry because of their advantages such as high emitting efficiency, narrow half-peak width, and continuously adjustable emitting wavelength. QDs light emitting diodes (QLEDs) are expected to become the next generation commercial display technology. This paper reviews the progress of QLED from physical mechanism, materials, to device engineering. The strategies to improve QLED performance from the perspectives of quantum dot materials and device structures are summarized. [ABSTRACT FROM AUTHOR]

The quality of the tin dioxide interface has an important impact on the performance of perovskite solar cells. Herein, a facile potassium acetate strategy to effectively treat the SnO2/perovskite interface and enhance the film quality of perovskite crystals is used. The defect density at the interface can be reduced, thereby suppressing the nonradiative recombination of excitons. Enhanced performance of the two‐step deposited perovskite device is obtained with an open‐circuit voltage (VOC) of 1.173 V, a fill factor of 78.31%, and a power conversion efficiency of 23.63%. [ABSTRACT FROM AUTHOR]