Highly Elastic and >200% Reversibly Stretchable Down‐Conversion White Light‐Emitting Diodes Based on Quantum Dot Gel Emitters

Abstract

electronics/optoelectronics, and artificial lighting technologies. [1] The advent of soft electronics has created a strong demand for the fabrication of highly flexible and stretchable WLEDs, [2] to support the development of advanced devices and systems with novel form factors. [3] In general, two main approaches, namely electroluminescence (EL) and photo luminescence (PL) or down-conversion, have been explored for fabricating white LEDs. [4] WLEDs based on EL have generated high expectations in the related research community in terms of efficiency and stability, and a few flexible light-emitting diodes (LEDs) have been reported. [5] However, the EL approach requires i) a multilayered structure design for transport/recombination of electrons and holes and ii) a complicated packaging process, which makes it hard to fabricate large-area devices in a cost-effective way. In particular, the multilayered structure contains interfaces of heterogeneous materials with different mechanical properties (e.g., elastic modulus and Poisson's ratio), which often result in mechanical failure under external stress. [3a,5a,6] On the other hand, down-conversion white LEDs have become increasingly popular in academic research and practical applications, due to their high performances and simple fabrication procedures. Owing to their high photostability, excellent color purity (with a narrow full width at half maximum, FWHM), high PL quantum yields (QYs, up to 100%), and color tunability from the ultraviolet to infrared region, semiconductor quantum dots (QDs) represent promising candidate materials for nextgeneration LEDs. [7] Various types of QDs encapsulated within solid matrices (e.g., silica particles, glass blocks, and polymer films) have been employed in down-conversion white LEDs, and high color rendering indexes (CRIs) and luminous efficacies (LEs) have been reported for LEDs based on InP/ZnS, carbon, perovskite, silicon, and cadmium-containing QDs. [8] However, owing to the poor mechanical reliability of the solid matrices, little progress has been made in developing stretchable down-conversion WLEDs using QDs. In addition, when the QDs are trapped into solid matrices, their performances, such as PL intensity and lifetime, usually decrease by 10-90% compared to those of QDs dispersed in liquid phases. [9] The Combining the characteristics of different materials offers exciting new opportunities for advanced applications in various fields. Herein, white lightemitting diodes (WLEDs) with >200% reversible stretchability are fabricated using six-color quantum dots (QDs) gel emitters. Stable aqueous-phase alloy core/shell QDs with high quantum yield are obtained via ligand exchange using a ternary solvent system. Transparent and highly stretchable gels with large pores are created by binary-solvent-based gelation at low temperatures. Importantly, the QDs and the gel originate from the same two solvents, which make the QDs highly compatible with the gelation process. Consequently, QDs of six different colors are incorpora...

Highly efficient emission and high-CRI warm white light-emitting diodes from ligand-modified CsPbBr₃ quantum dots

“…In addition, it is worth pointing out that the full-width at half-maximum (FWHM) of the red-emitting component is a very important factor for realizing high performance WLEDs [48][49][50][51] . In terms of the optionally red-emission materials for the WLEDs, the red-emission CsPbI 3 perovskite QDs suffer from poor stability and narrow FWHM of the emission spectrum 52,53 .…”

Rare Earth‐Free Luminescent Materials for WLEDs: Recent Progress and Perspectives

“…d-e) Adapted with permission. [35] Copyright 2020, Wiley-VCH. f) Emission spectra of various modified g-C 3 N 4 -based LEDs and photographs of the working devices.…”

“…Moreover, this material was able to withstand 200% elastic deformation and maintain the original luminous performance after more than 1000 bending/ stretching cycles, which is impossible for traditional rare-earth luminescent powders (Figures 2d,e). [35] The aforementioned composite materials based on QDs have good luminescence properties, but many of them contain toxic elements such as Cd, which limits their potential applications.…”

Ultra-Stretchable and Self-Healing Anti-Freezing Strain Sensors Based on Hydrophobic Associated Polyacrylic Acid Hydrogels

“…Based on these intrinsic traits, hydrogels have developed a lot of applications in different fields, such as in flexible electronics [3], drug delivery [4], tissue engineering [5], waste treatment [6,7], and superabsorbent materials [8]. Due to the outstanding performance in artificial nerves [9], flexible robotics [10], solid electrolytes [11][12][13][14], conductors [15], tactile sensors [16], environment sensors [17,18], human-machine interface [9,19], optoelectronics [20,21], and energy applications [22][23][24][25], flexible electronics have earned more extensive and particular attention during practical utilization [26].…”