Mg-doped ZnO (ZMO) nanocrystal (NC) has been widely used as an electron transport layer (ETL) in quantum dot (QD) light-emitting diodes (QLEDs). However, its abundant oxygen vacancy (O_V) defects, high chemical activity and poor reproducibility of synthesis severely degrade device performance and shelf stability, limiting the practical application in display. To address these challenges, high-quality Sn⁴⁺/Mg²⁺ co-doped ZnO (ZMSO) NCs were synthesized via a microfluidic (MF) reactor in the present study. This co-doping strategy effectively suppresses the O_V defects formation, increases the conduction band and electrical resistivity to enhance charge balance, as well as enhances the chemical stability of NCs to mitigate unstable chemical reaction during storage. Furthermore, the MF synthesis of NCs ensured consistent reproducibility and scalability. Based on the new ZMSO-based ETL, a remarkable enhancement of ZnSeTe blue QLED performance has been achieved, with a 2-fold increase in external quantum efficiency (EQE) from 9.6% to 19.7% and a 4.6-fold improvement in lifetime (@100 cd·m⁻²) from 3931 to 18,236 h. Notably, the ZMSO-based device exhibited lower efficiency roll-off at high luminance and superior shelf stability compared to ZMO-based devices, offering an effective approach to achieving highly efficient and stable Cd-free blue QLEDs toward practical applications.

Flexible electrochromic devices (FECDs) are promising candidates for the next generation of wearable electronics due to their low operating voltage and energy consumption. For the flexible electrochromic devices, the electrolyte is an important component. Typically, the electrolyte needs to be formulated according to the device structure and usage scenario. A high-performance electrolyte involves consideration of many factors, including choosing the right polymer, solvent, curing agent, and ion type to satisfy particular device specifications. In this work, a ultraviolet-curable solid–liquid host–guest (UV-SLHG) electrolyte is developed. Several aspects of performance are improved by introducing the solid–liquid coexisting microstructure without changing the electrolyte formulation, including excellent adhesion, a 30% increase in tensile characteristics, and a seven-fold increase in ionic conductivity when compared to a fully cured solid-state electrolyte. More importantly, the unique advantage of SLHG electrolytes lies that the thickness will not change significantly during bending. The FECD made by using the UV-SLHG-based electrolyte sustained 10,000 bending cycles at the bending radius of 2.5 mm while maintaining outstanding optical modulation. A wearable ring-type ECD and a battery-free FECD wine label were made as demonstrators. The UV-SLHG strategy is not only suitable for the FECDs but also universally applicable to other electrolyte-based of flexible electronics such as flexible capacitors and batteries.

Poly[(9, 9-dioctylfluorenyl-2, 7-diyl)-alt(4, 4'-(N-(4-butylphenyl))] (TFB), one of the most popular and widely used hole-transport layer (HTL) materials, has been successfully applied in high performance spin-coated quantum dots-based light-emitting diodes (QLEDs) due to its suitable energy level and high mobility. However, there are still many challenging issues in inkjet-printed QLED devices when using TFB as HTL. TFB normally suffers from the interlayer mixing and erosion, and low surface energy against the good film formation. Here, a novel environment-friendly binary solvent system was established for formulating quantum dot (QD) inks, which is based on mixing halogen-free alkane solvents of decalin and n-tridecane. The optimum volume ratio for the mixture of decalin and n-tridecane was found to be 7:3, at which a stable ink jetting flow and coffee-ring free QD films could be formed. To research the influence of substrate surface on the formation of inkjet-printed QD films, TFB was annealed at different temperatures, and the optimum annealing temperature was found to enable high quality inkjet-printed QD film. Inkjet-printed red QLED was ultimately manufactured. A maximum 18.3% of external quantum efficiency (EQE) was achieved, reaching 93% of the spin-coated QLED, which is the best reported high efficiency inkjet-printed red QLEDs to date. In addition, the inkjet-printed QLED achieved similar T₇₅ operational lifetime (27 h) as compared to the spin-coated reference QLED (28 h) at 2, 000 cd·m⁻². This work demonstrated that the novel orthogonal halogen-free alkane co-solvents can improve the interfacial contact and facilitate high-performance inkjet printing QLEDs with high EQE and stability.