Metal-halide perovskite-based green and red light-emitting diodes (LEDs) have witnessed a rapid development because of their facile synthesis and processability; however, the blue-band emission is constrained by their unstable chemical properties and poorly conducting emitting layers. Here, we show a trioctylphosphine oxide (TOPO)-mediated one-step approach to realize bright deep-blue luminescent FAPbBr3 nanoplatelets (NPLs) with enhanced stability and charge transport. The concentration of NPL surface ligands is shown to be progressively tuned via varying the amount of intermediate TOPO due to the acid–base equilibrium between protic acid and TOPO. By effectively optimizing the concentration of surface ligands, the structural integrity of NPL solids can be preserved in ambient air for a week, mainly because of the highly ordered and dense solid assembly and the reduced defects. The removal of excess organic ligands also enables the improvement of charge mobility by orders of magnitude. Ultimately, ultrapure deep-blue perovskite LEDs (439 nm) with a narrow emission width of 14 nm and a peak EQE of 0.14% are achieved at low driving voltage. Our finding expands the current understanding of surface ligand modulation in the development of pure bromide deep-blue perovskite optoelectronics.

Recently, lead sulfide (PbS) quantum dots (QDs) have demonstrated great potential in becoming one of the most promising next-generation photoelectrical materials for photodetectors. PbS QDs provide fascinating properties including size-controllable spectral sensitivity, a wide and tunable absorption range, cost-efficient solution processability, and flexible substrate compatibility. One of the key problems that limit the performance of PbS QDs-based photodetectors is inefficient carrier transfer. Long ligands decorating the outside surface of PbS QDs to protect them against degeneration inhibit the transfer of electrical charge carriers and thereby limit the device performance. To overcome this problem, the long ligands need to be effectively exchanged. Here, a two-step ligand-exchange method is demonstrated. The QDs are pretreated using methylammonium iodide in solution as the first step ligand exchange before the layer-by-layer deposition process and solid-state ligand exchange. The grazing-incidence small-angle X-ray scattering and X-ray photoelectron spectroscopy analyses prove a smaller spacing among the QDs and an increased ligand-exchange ratio by adopting the two-step method. This strongly indicates a better capability of charge transfer than the traditional one-step solid-state ligand-exchange technology. Devices fabricated using the two-step method present an enhancement of the charge-transfer capability with a larger current. The efficient charge transfer is further demonstrated by a significant 94% increase of the responsivity and a 57% enhancement of the detectivity of the PbS QDs-based photodetector, reaching 3302 mA/W and 5.06 × 1012 J, respectively.

Colloidal nanoplatelets (NPLs) are an emerging semiconductor nanocrystal in the display community due to their ultranarrow emission linewidth. Herein, an ultrapure green emitting nanocrystal light‐emitting diode (LED) based on four‐monolayer CdSe/CdS core/crown NPLs is developed. By applying the nonstacked nanoplates, the nonradiative energy transfer in the NPLs film is successfully suppressed. The nonstacked NPL‐LEDs with pure green emission of 521.5 nm exhibit a low turn‐on voltage of 2.1 V, a maximum luminance of 22 400 cd m−2, a peak external quantum efficiency (EQE) of 2.16%, which is a sixfold enhancement comparing to the stacked NPL‐LED (EQE = 0.34%). This work demonstrates the potential of core/crown NPLs for ultrawide color gamut displays.

A modified supersaturated recrystallization method for in situ fabrication of Cs4PbBr6/CsPbBr3 nanocomposite containing polymer films is reported. This facile and efficient strategy can be easily carried out at room temperature, and minimizes the contact time between CsPbBr3 nanocrystals and water and oxygen molecules during the formation of perovskite film, passivating the perovskite nanocrystals. Through the approach, the dual protection of Cs4PbBr6 and polymer matrix enhances the water stability and photostability of emitting CsPbBr3. Even after being immersed in water for 30 days, the Cs4PbBr6/CsPbBr3@PMMA film still retains a bright green fluorescence. Moreover, combining the as‐prepared green‐emitting Cs4PbBr6/CsPbBr3@PMMA and a red‐emitting CdSe/ZnS based quantum dots (QDs) polymer film with blue light emitting diode (LED) chips as the backlight, a high performance liquid crystal display (LCD) is demonstrated. The color gamut of the demonstrated display is 131% and 98% that of the NTSC 1953 and Rec.2020, respectively. The combination of better stability and improved color purity of the perovskite material intuitively provides a viable approach for LCD backlights.

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Quantum dot light-emitting diodes (QLEDs) possess huge potential in display due to their outstanding optoelectronic performance; however, serve degradation during operation blocks their practical applications. High temperature is regarded as one of major factors causing degradation. Therefore, a systematical study on the working temperature of QLEDs is very essential and urgent for the development of high stable QLEDs. In this work, different influence factors such as the electro-optic conversion efficiency (EOCE), voltage, current density, active area, substrate size, substrate type and sample contact are discussed in detail on the working temperature of QLEDs. The research results show that the working temperature of general QLEDs under normal operation conditions is usually smaller than 75 °C when the ambient temperature is 25 °C. However, temperature of QLEDs working under extreme conditions, such as high power or small substrate size, will exceed 100 °C, resulting in irreversible damage to the devices. Moreover, some effective measures to reduce the working temperature are also proposed. The analysis and discussion of various influencing factors in this work will provide guidance for the design of stable QLEDs and help them work at a safer temperature.

With the economic and social developments, the demand for higher quality displays has always remained strong. The emerging 8K displays represent an advancement of ultra-high resolution. Other parameters such as the contrast ratio and viewing angle were all improved significantly. Here, we would like to address the recent efforts in the color (color gamut) of displays toward an ultra-wide color gamut, which we call the ‘color revolution’. In the past few years, fluorescent semiconductor quantum dots, quantum rods, fluorescent perovskite nanocrystals, and nanoplatelets with narrow emission have been discovered, and have been explored in display technologies as photoluminescent enhancement films, color convertors, or electroluminescent emissive layers. As a result, the color gamut of display technologies was broadened remarkably, enabling the color revolution. Here, we provide a review of this exciting progress iin the color revolution.

We present a large‐scale transparent luminance enhancement film with quantum rods aligned in polymeric nanofibers by electrospinning for high efficiency wide color gamut LED display. 18.4% brightness enhancement is achieved for LED display using aligned QR film with 0.45 polarization over an area of 5 cm2.