Huanhuan Deng

Bio: Huanhuan Deng is an academic researcher from Beihang University. The author has contributed to research in topics: Materials science & Supercooling. The author has an hindex of 1, co-authored 3 publications receiving 4 citations.

Direct-Writing Large-Area Cross-Aligned Ag Nanowires Network: Toward High-Performance Transparent Quantum Dot Light-Emitting Diodes

Abstract: Flexible transparent electrodes (FTEs) made of silver nanowires (AgNWs) have been widely used in wearable and foldable electronics devices. For obtaining FTEs with both high transparency and low re...

Controllable patterning of nanoparticles via solution transfer processes

Abstract: Solution processes have been widely used in controllable patterning of zero-dimensional nanoparticles on certain substrates due to their advantages of mild conditions, low-cost fabrication and good device compatibility. Preparing high-quality micro-patterns is very important for realizing high-performance devices. However, the solution processes normally involve both the coffee ring effect and Marangoni flow caused by solvent evaporation, which make it hard for precisely patterning nanoparticles in a controllable manner, leading to nonuniform micro-patterns. Therefore, various approaches have been developed to solve the adverse effects of the coffee ring during the film-forming process. In this contribution, we have reviewed the recent progress in controllable patterning of nanoparticles using solution transfer approaches either by taking advantage of or by inhibiting the coffee ring effect, as well as the mechanism involved and the applications in various fields.

Direct Writing Large-Area Multi-Layer Ultrasmooth Films by an All-Solution Process: Toward High-Performance QLEDs.

Abstract: With increasing the film area/layer, deteriorating in both smoothness and uniformity of thin-films frequently happen, which remains a barrier for making large-area quantum dot light-emitting diodes (QLEDs) by solution processes. Here, we demonstrated a facile all-solution process guided by the conical fiber array to write multi-layer ultrasmooth thin-films directly in centimeter scale. The side-by-side fibrous array helps to align surface tensions at the tri-phase contact line to facilitate large-area homogeneous deposition, which was verified by theoretical simulation. The Laplace pressure along individual conical fiber contributes to the steady liquid transfer. Thin-films with small roughness (<2.03 nm) and large-area (2×2 cm2 ) uniformity were prepared sequentially on the target substrate, leading to large-area high-performance QLEDs. The result offers new insights for fabricating large-area high-performance thin-film devices.

Activating Energy Transfer Tunnels by Tuning Local Electronegativity of Conjugated Polymeric Backbone for High‐Efficiency OLEDs with Low Efficiency Roll‐Off

Abstract: Thermally activated delayed fluorescence (TADF) conjugated polymers are attractive for display and illumination applications owing to their excellent device performance and convenient device fabrication. However, conjugated polymers frequently encounter insufficient energy transfer from hosts to TADF units, lowering device performance. Herein, a strategy for improving light‐emitting performances through adjusting the local electronegativity of the polymeric backbones by inserting electron‐withdrawing atoms and activating energy transmission channels is proposed. Meanwhile, strongly electronegative atoms also affect the charge‐transfer natures (CT) of TADF polymers and minimize the energy difference between the lowest singlet and triplet states, leading to a rapid reverse intersystem crossing process through the vibronic coupling between 1CT and 3CT with extremely close energy levels. The produced TADF polymer, pBP‐PXZ, can achieve an external quantum efficiency (EQE) of 23.11%, exhibiting no roll‐off when the luminance is less than 200 cd m−2 whereas only a 3% EQE decrease at 500 cd m−2. The EQE can even maintain above 19% under 1000 cd m−2, which is the highest efficiency among TADF polymer‐based organic light‐emitting diodes (OLEDs) under high luminance. The study provides a new perspective for designing high‐performance OLEDs materials.

2D All-Solid-State Fabric Supercapacitor Fabricated Via an All Solution Process for Use in Smart Textiles

Abstract: We propose a method to fabricate a supercapacitor for smart textiles using silver (Ag) nanoparticle (NP) ink, simple spray patterning systems, and intense pulsed light (IPL) sintering systems. The Ag NP current collectors provided as high conductivity as the metal current collectors. The spray patterning technique is useful for fabricating supercapacitors because it is simple, fast, and cheap. IPL systems reduced the sintering temperature of Ag NPs and prevented thermal damage to the textiles during the Ag NP sintering process. The two-dimensional (2D) all-solid state fabric supercapacitor with an interdigitated configuration, developed here, exhibited a specific capacitance of 25.7 F/g and an energy density of 1.5 Wh/kg at a power density of 64.3 W/kg. These results support the utility of our proposed method in the development of energy textiles.

Marangoni flow and surfactant transport in evaporating sessile droplets: A lattice Boltzmann study

Abstract: The circulatory Marangoni flow can alter the contact line deposition in evaporating colloidal droplets with pinned contact line. Marangoni flow can be induced by surfactants or thermal effects. Although both cases have been exclusively investigated, the combined effect of surfactant-induced and thermal Marangoni flows is still unknown. The lattice Boltzmann method is utilized to simulate droplet evaporation and corresponding Marangoni flow. Five equations for hydrodynamics, interface capturing, vapor concentration, temperature field, and surfactant transport are intrinsically coupled with each other. They are simultaneously solved in the lattice Boltzmann framework. A geometrical method is proposed to pin the contact line at the triple point. First, evaporation-induced and thermal Marangoni flows are successfully captured. By incorporating surfactant-induced effects, interesting flow patterns are observed. Considering the combined effect of surfactant and temperature gradient, maximum surfactant concentration and maximum temperature (local minima for surface tension) are found at the top and the edge of the droplet, respectively. The maximum surface tension is consequently located between them, and double-circulation flow is observed. If the thermal effect is eliminated, surfactant local concentrations intermittently converge to steady values so that the edge concentration becomes higher than the apex concentration. Until reaching the steady state, there are two patterns that the flow alternates between: one in the direction of the thermal Marangoni flow and the other in the opposite direction.

Controllable patterning of nanoparticles via solution transfer processes

Abstract: Solution processes have been widely used in controllable patterning of zero-dimensional nanoparticles on certain substrates due to their advantages of mild conditions, low-cost fabrication and good device compatibility. Preparing high-quality micro-patterns is very important for realizing high-performance devices. However, the solution processes normally involve both the coffee ring effect and Marangoni flow caused by solvent evaporation, which make it hard for precisely patterning nanoparticles in a controllable manner, leading to nonuniform micro-patterns. Therefore, various approaches have been developed to solve the adverse effects of the coffee ring during the film-forming process. In this contribution, we have reviewed the recent progress in controllable patterning of nanoparticles using solution transfer approaches either by taking advantage of or by inhibiting the coffee ring effect, as well as the mechanism involved and the applications in various fields.