Polyacrylamide gels with different stiffness and glass were employed as substrates to investigate how substrate stiffness affects the cellular stiffness of adherent hepatocellular carcinoma (HCCLM3) and hepatic (L02) cells. The interaction of how cell-substrate stiffness influences cell migration was also explored. An atom force microscope measured the stiffness of HCCLM3 and L02 cells on different substrates. Further, F-actin assembly was analyzed using immunofluorescence and Western blot. Finally, cell-surface expression of integrin β1 was quantified by flow cytometry. The results show that, while both HCCLM3 and L02 cells adjusted their cell stiffness to comply with the stiffness of the substrate they were adhered to, their tuning capabilities were different. HCCLM3 cell stiffness complied when substrate stiffness was between 1.1 and 33.7 kPa, whereas the analogous stiffness for L02 cells occurred at a higher substrate stiffness, 3.6 kPa up to glass. These ranges correlated with F-actin filament assembly and integrin β1 expression. In a migration assay, HCCLM3 cells migrated faster on a relatively soft substrate, while L02 cells migrated faster on substrates that were relatively rigid. These findings indicate that different tuning capabilities of HCCLM3 and L02 cells may influence cell migration velocity on substrates with different stiffness by regulating cy- toskeleton remodeling and integrin β1 expression.

Optimization of ink-jet printing conditions of quantum-dot (QD) ink by cosolvent process and improvement of quantum-dot light-emitting diodes (QLEDs) characteristics assisted by vacuum annealing were analyzed in this research. A cosolvent process of hexane and ortho-dichlorobenzene (oDCB) was optimized at the ratio of 1:2, and ink-jetting properties were analyzed using the Ohnesorge number based on the parameters of viscosity and surface tension. However, we found that these cosolvents systems cause an increase in the boiling point and a decrease in the vapor pressure, which influence the annealing characteristics of the QD emission layer (EML). Therefore, we investigated QLEDs’ performance depending on the annealing condition for ink-jet printed QD EML prepared using cosolvents systems of hexane and oDCB. We enhanced the quality of QD EML and device performance of QLEDs by a vacuum annealing process, which was used to prevent exposure to moisture and oxygen and to promote effective evaporation of solvent in QD EML. As a result, the characteristics of QLEDs formed using ink-jet printed QD EML annealed under vacuum environment increased luminescence (L), current efficiency (CE), external quantum efficiency (EQE), and lifetime (LT50) by 30.51%, 33.7%, 21.70%, and 181.97%, respectively, compared to QLEDs annealed under air environment.

In this study, we introduce optimization of the annealing conditions for improvement of hardness and hole transporting properties of high-molecular weight poly [9, 9-dioctylfluorene-co-N-(4-(3-methylpropyl)) diphenylamine] (TFB) film used as a Hole Transport Layer (HTL) of Quantum-dot Light-emitting Diodes (QLEDs). As annealing temperatures were increased from 120 °C to 150 °C or more, no dissolving or intermixing phenomena at the interface between HTL and Quantum-Dot Emission Layer (QDs EML) was observed. However, when the annealing temperatures was increased from 150 °C to 210 °C, the intensity of the absorbance peaks as determined by Fourier Transform Infrared (FT-IR) measurement was found to relatively decrease, and hole transporting properties were found to decrease in the measurement of current density - voltage (CD - V) and capacitance - voltage (C - V) characteristics of Hole Only Devices (HODs) due to thermal damage. At the annealing temperature of 150 °C, the QLEDs device was optimized with TFB films having good hardness and best hole transporting properties for solution processed QLEDs.

Organic-inorganic hybrid perovskite materials have attracted tremendous attention as a key material in various optoelectronic devices. Distinctive optoelectronic properties, such as a tunable energy band position, long carrier diffusion lengths, and high charge carrier mobility, have allowed rapid progress in various perovskite-based optoelectronic devices (solar cells, photodetectors, light emitting diodes (LEDs), and lasers). Interestingly, the developments of each field are based on different characteristics of perovskite materials which are suitable for their own applications. In this review, we provide the fundamental properties of perovskite materials and categorize the usages in various optoelectronic applications. In addition, the prerequisite factors for those applications are suggested to understand the recent progress of perovskite-based optoelectronic devices and the challenges that need to be solved for commercialization.

We investigated the effect of intense-pulsed light (IPL) post-treatment on the time-dependent characteristics of ZnO nanoparticles (NPs) used as an electron transport layer (ETL) of quantum-dot light-emitting diodes (QLEDs). The time-dependent characteristics of the charge injection balance in QLEDs was observed by fabrication and analysis of single carrier devices (SCDs), and it was confirmed that the time-dependent characteristics of the ZnO NPs affect the device characteristics of QLEDs. Stabilization of the ZnO NPs film properties for improvement of the charge injection balance in QLEDs was achieved by controlling the current density characteristics via filling of the oxygen vacancies by IPL post-treatment.