Multi-color light-emitting diodes (LEDs) with various advantages of color tunability, self-luminescence, wide viewing angles, high color contrast, low power consumption, and flexibility provide a wide range of applications including full-color display, augmented reality/virtual reality technology, and wearable healthcare systems. In this review, we introduce three main types of multi-color LEDs: the organic LED, colloidal quantum dots (CQDs) LED, and CQD–organic hybrid LED. Various strategies for realizing multi-color LEDs are discussed including red, green, and blue sub-pixel side-by-side arrangement; vertically stacked LED unit configuration; and stacked emitter layers in a single LED. Finally, according to their status and challenges, we present an outlook of multi-color devices. We hope this review can inspire researchers and make a contribution to the further improvement of multi-color LED technology.

Optoelectronic devices integrated with multiple functions for interactive signal visualization have become increasingly important in the intelligent era. Here, a color‐tunable organic light‐emitting diode (CTOLED) is developed to achieve a user‐interaction intelligent device that enables multicolor visualization of infrared light and temperature distribution via the modulation with a multi‐stimuli responsive silicon (Si) sensor for the first time. The key to the color‐tunable functionality of the CTOLED is an ultrathin exciton‐blocking layer between different emitting layers, which leads to the quantitative correlation of driving current and emitted visible color. As a result, the user can manipulate the silicon/color‐tunable organic light‐emitting diode (Si/CTOLED) device through the infrared pen, and the “writing” spatial information and the infrared intensity can influence the display patterns and colors. Besides, the temperature is sensed by the flexible Si/CTOLED device and is displayed in corresponding different colors, which is promising as a wearable temperature visualization monitor and directly interact with a user. The temperature monitor exhibits ultrasensitivity with a low minimum distinguishable temperature difference of only 65 mK. The Si/CTOLED devices open new possibilities for the development of intelligent devices and have promising multi‐disciplinary applications.

Understanding the mapping relationship between electrochemical characteristics and physicochemical properties of layered LiNi0.80Co0.15Al0.05O2 (NCA) cathodes is important to develop high energy density lithium‐ion batteries (LIBs). Combining in situ and ex situ characterization, the effect of the H2‐H3 phase transition on the capacity decay and aging mechanism of NCA materials are systematically investigated. With the increase of cut‐off voltage, the cathode electrolyte interphase (CEI) on the NCA interface shows an evolutionary path of formation‐thickening‐rupture. This phenomenon is closely related to the H2‐H3 phase transition. The volumetric stresses and strains caused by the H2‐H3 phase transition accelerate the formation and expansion of secondary particle microcracks in the electrode material, leading to the growth of interfacial CEI variations. The capacity of the electrode material can decrease even if the material does not experience the H2‐H3 phase transition due to the persistence of interfacial side reactions with calendar aging from long cycles. This work opens up a valuable perspective for the study of the mapping relationship between phase transition and electrochemical properties in Ni‐rich layered oxide cathodes and provides guidance for developing high capacity and long cycle life LIBs.

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