Colloidal quantum wells (CQWs) have emerged as a promising family of two-dimensional (2D) optoelectronic materials with outstanding properties, including ultranarrow luminescence emission, nearly unity quantum yield, and large extinction coefficient. However, the performance of CQWs-based light-emitting diodes (CQW-LEDs) is far from satisfactory, particularly for deep red emissions (≥660 nm). Herein, high efficiency, ultra-low-efficiency roll-off, high luminance, and extremely saturated deep red CQW-LEDs are reported. A key feature for the high performance is the understanding of charge dynamics achieved by introducing an efficient electron transport layer, ZnMgO, which enables balanced charge injection, reduced nonradiative channels, and smooth films. The CQW-LEDs based on (CdSe/CdS)@(CdS/CdZnS) ((core/crown)@(colloidal atomic layer deposition shell/hot injection shell)) show an external quantum efficiency of 9.89%, which is a record value for 2D nanocrystal LEDs with deep red emissions. The device also exhibits an ultra-low-efficiency roll-off and a high luminance of 3853 cd m −2 . Additionally, an exceptional color purity with the CIE coordinates of (0.719, 0.278) is obtained, indicating that the color gamut covers 102% of the International Telecommunication Union Recommendation BT 2020 (Rec. 2020) standard in the CIE 1931 color space, which is the best for CQW-LEDs. Furthermore, an active-matrix CQW-LED pixel circuit is demonstrated. The findings imply that the understanding of charge dynamics not only enables high-performance CQW-LEDs and can be further applied to other kinds of nanocrystal LEDs but also is beneficial to the development of CQW-LEDs-based display technology and related integrated optoelectronics.

Organic light-emitting diodes (OLEDs) have great potential for display, lighting, and near-infrared (NIR) applications due to their outstanding advantages such as high efficiency, low power consumption, and flexibility. Recently, it has been found that the ultrathin emitting nanolayer technology plays a key role in OLEDs with simplified structures through the undoped fabricated process, and exciplex-forming hosts can enhance the efficiency and stability of OLEDs. However, the elementary structure and mechanism of the energy transfer process of ultrathin emitting nanolayers within interface exciplexes are still unclear. Therefore, it is imminently needed to explore the origin of ultrathin emitting nanolayers and their energy process within exciplexes. Herein, the mechanism of films growing to set ultrathin emitting nanolayers (<1 nm) and their energy transfer process within interface exciplexes are reviewed and researched. The UEML phosphorescence dye plays a key role in determining the lifetime of excitons between exciplex and non-exciplex interfaces. The exciplex between TCTA and Bphen has longer lifetime decay than the non-exciplex between TCTA and TAPC, facilitating exciton harvesting. The findings will be beneficial not only to the further development of OLEDs but also to other related organic optoelectronic technologies.

lasers, photodetectors, and light-emitting diodes (LEDs) thanks to the excellent properties, including high photoluminescence quantum yield (PLQY), narrow emissions, size-tunable optical bandgaps, and excellent charge-transport capabilities. [1][2][3][4][5] Since the first successful room-temperature report of hybrid organic-inorganic CH 3 NH 3 PbBr 3 perovskite LED (PeLED) in 2014, [6] PeLEDs have rapidly attracted a great deal of attention from both academic and industrial researchers. [7][8][9][10] To date, the highest external quantum efficiency (EQE) for green, red, and near-infrared PeLEDs can overtake 20%, which is comparable to

Colloidal quantum wells (CQWs) are regarded as a frontier class of light‐emitting diodes (LEDs) owing to their efficient and ultranarrow luminescence spectrum, directional emission, and high light extraction. However, CQW‐LEDs with deep‐red (> 660 nm) light emission, a vital part for high‐definition color displays, optical medical, and horticultural lighting, remain a great challenge. Herein, high‐efficiency deep‐red CQW‐LEDs are reported. With the enhancement of device engineering, the LED devices that based new CQW materials have shown high external quantum efficiency of 9.89%. Additionally, Mg‐doped zinc oxide (ZnMgO) and In2O3 as electron transport layer (ETL) are introduced into CQW‐LEDs for the first time, and the effect of different ETLs on carrier injection balance of CQW‐LEDs is investigated. Furthermore, the first prototype active‐matrix CQW‐LED (AMCQW‐LED) pixel circuit was constructed by connecting thin film transistor (TFT) source terminal with CQW‐LED. The findings may not only begin the first step that TFT drives CQW‐LED, but also reveal the carrier injection balance mechanism of CQW‐LEDs, and can be further applied to other wavelengths of CQW‐LEDs.

Despite substantial progress has been achieved in red/near‐infrared, green, and blue perovskite light‐emitting diodes (PeLEDs), studies on cyan emitting perovskites are still lacking. However, cyan‐emitting perovskite materials are of great importance and have many promising applications, especially for high‐quality lighting and light communication. Herein efficient cyan‐blue PeLEDs simultaneously achieving high luminance and high color stability are fabricated by using a bifunctional ligand, L‐Phenylalanine Methyl ester hydrochloride (L‐PMEH). It reveals the carboxyl and amine groups would heal charged defects via electrostatic interactions, and the neutral chlorine related defects can be reduced by the aromatic structures. The optimized cyan‐blue PeLEDs show a maximum external quantum efficiency (EQE) of 6.17% with an emission peak at 497 nm and a full width at half‐maximum of 21 nm as well as CIE coordinates of (0.09, 0.19). The obtained maximum luminance of 6347 cd m–2 is one of the highest values among the efficient and color‐stable cyan‐blue PeLEDs.