Light-Emitting Textiles: Device Architectures, Working Principles, and Applications

E-textiles represent an emerging technology aiming toward the development of fabric with augmented functionalities, enabling the integration of displays, sensors, and other electronic components into textiles. Healthcare, protective clothing, fashion, and sports are a few examples application areas of e-textiles. Light-emitting textiles can have different applications: sensing, fashion, visual communication, light therapy, etc. Light emission can be integrated with textiles in different ways: fabricating light-emitting fibers and planar light-emitting textiles or employing side-emitting polymer optical fibers (POFs) coupled with light-emitting diodes (LEDs). Different kinds of technology have been investigated: alternating current electroluminescent devices (ACELs), inorganic and organic LEDs, and light-emitting electrochemical cells (LECs). The different device working principles and architectures are discussed in this review, highlighting the most relevant aspects and the possible approaches for their integration with textiles. Regarding POFs, the methodology to obtain side emissions and the critical aspects for their integration into textiles are discussed in this review. The main applications of light-emitting fabrics are illustrated, demonstrating that LEDs, alone or coupled with POFs, represent the most robust technology. On the other hand, OLEDs (Organic LEDs) are very promising for the future of light-emitting fabrics, but some issues still need to be addressed.

Progress toward blue-emitting (460–475 nm) nanomaterials in display applications

Recently, quantum dots (QD) and quantum rods (QRs) have become extremely popular in displays and lighting applications. Liquid crystal displays (LCDs) equipped with quantum dot enhancement films (QDEFs) offer extended color saturation, increasing said saturation from 60 to 70% to more than 100% of the NTSC color gamut. A plethora of research dealing with EL/PL properties and the device-based performance of these materials has been published. The tunable emission wavelength and the narrow emission bandwidth are the key features of quantum dots and perovskite nanoparticles that primarily depend on the nanoparticle size and material composition. QRs, in contrast, have a core–shell structure and emit polarized light that can roughly double the efficiency of modern displays. However, blue emission for QRs, because of the large bathochromic redshift during shell growth, is a serious problem. Besides photoluminescence, electroluminescence is also important for display applications. These QD-LEDs show a lower turn ON voltage in comparison to organic LEDs, which is very important for high-resolution displays. The solution-processed narrower emission QD-LEDs have already achieved efficiency and a brightness comparable to vacuum-deposited phosphorescent organic LEDs (OLEDs). However, the blue-emitting nanoparticles and their short operational lifetime are the key obstacles in the progression of these devices. Furthermore, recently the display and lighting industry are trying to reduce the short-wavelength emissions, particularly in the spectral region below 455 nm, which has a much greater impact on human ocular health and circadian rhythm. Thus, industries are aiming at blue light in the spectral range of 460–475 nm. This spectral range is very challenging for nanomaterials because of the limited choice of materials. In this review, we summarize the recent progress made in the blue-emitting nanomaterials with a different morphology and composition. This includes recent developments in low Cd materials. Both the PL and EL properties of these materials have been discussed depending on the NP’s shape and material composition. This review also aims to discuss the various device architectures employing blue-emitting NPs, any recent achievements and future challenges.

Advances in Perovskite Light-Emitting Diodes Possessing Improved Lifetime

Recently, perovskite light-emitting diodes (PeLEDs) are seeing an increasing academic and industrial interest with a potential for a broad range of technologies including display, lighting, and signaling. The maximum external quantum efficiency of PeLEDs can overtake 20% nowadays, however, the lifetime of PeLEDs is still far from the demand of practical applications. In this review, state-of-the-art concepts to improve the lifetime of PeLEDs are comprehensively summarized from the perspective of the design of perovskite emitting materials, the innovation of device engineering, the manipulation of optical effects, and the introduction of advanced encapsulations. First, the fundamental concepts determining the lifetime of PeLEDs are presented. Then, the strategies to improve the lifetime of both organic-inorganic hybrid and all-inorganic PeLEDs are highlighted. Particularly, the approaches to manage optical effects and encapsulations for the improved lifetime, which are negligibly studied in PeLEDs, are discussed based on the related concepts of organic LEDs and Cd-based quantum-dot LEDs, which is beneficial to insightfully understand the lifetime of PeLEDs. At last, the challenges and opportunities to further enhance the lifetime of PeLEDs are introduced.