High-Performance Deep Red Colloidal Quantum Well Light-Emitting Diodes Enabled by the Understanding of Charge Dynamics

Abstract

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.

Ionic Liquid-Gated Near-Infrared Polymer Phototransistors and Their Persistent Photoconductivity Application in Optical Memory

“…The transfer curve in the saturation region (V DS is −0.8 V and V G is swept from 2.0 to −1.0 V at a speed of 10 mV/s) displays very good switching characteristics, and the on/off source-drain current (I DS ) ratio is up to 1.03 × 10. 3 The gate leakage currents (I G ) in the dark from 2.0 to −1.0 V are lower than 20 nA (Figure S2c), which can guarantee the normal device operation of the ILGOPTs. The transconductance (g m ) is up to 3.01 μS.…”

“…The output curves exhibit gate voltage regulation characteristics, and there are obvious linear and saturation regions, which indicate that the working mechanism of the resulting PCDTPT-based ILGOPTs is dominated by the electric double layer (EDL) mode. The transfer curve in the saturation region ( V DS is −0.8 V and V G is swept from 2.0 to −1.0 V at a speed of 10 mV/s) displays very good switching characteristics, and the on/off source-drain current ( I DS ) ratio is up to 1.03 × 10 . The gate leakage currents ( I G ) in the dark from 2.0 to −1.0 V are lower than 20 nA (Figure S2c), which can guarantee the normal device operation of the ILGOPTs.…”

“…Organic semiconductors have paved the way toward development of the novel optoelectronic devices with the integration of multiple functions, such as light-emission, − detection, switching, and storage, which greatly broadens the application range of the devices. As a new class of organic multifunctional device, organic phototransistors (OPTs), the combination of organic transistors and photodetectors, have received extensive attention in recent years. ,− The OPT, a three-terminal photoresponsive device, exhibits higher photosensitivity and lower noise ,, compared with the common two-terminal photodetectors due to the current amplification effect of the gate terminal of the transistor.…”

Atomically flat semiconductor nanoplatelets for light-emitting applications

“…8,9,18 These fascinating properties in combination with the precise morphology and structure control of NPLs at the atomic level provide a solid basis for their potential in high color purity light-emitting applications. [18][19][20][21][22] Being different from semiconductor quantum wells synthesized by chemical vapor deposition and molecular beam epitaxy, which require high vacuum and expensive instruments, semiconductor NPLs can be feasibly prepared using colloidal wet chemical methods, which means that they can be made using comparatively inexpensive processes and their syntheses are scalable.…”

Polyimide Layers with High Refractivity and Surface Wettability Adapted for Lowering Optical Losses in Solar Cells

“…However, incorporating low polarizable units reduces the refractive index closer to that of a classical cover glass, which enlarges the TIR-derived optical losses at the cover/electrode interface. The use of highly refractive PIs can be extended to LED devices, which currently are aimed at better performances by incorporating an efficient electron transport layer [ 21 ]. PIs can be used as flexible substrates for LEDs due to their thermal resistance and flexibility [ 22 , 23 ].…”