Laser speckle formed disordered micro-meander structures for light extraction enhancement of flexible organic light-emitting diodes

Enhanced performance of organic light-emitting diodes by integrating quasi-periodic micro-nano structures

To integrate a quasi-periodic micro-nano structure (PMS) to the organic light-emitting devices (OLEDs) is an efficient way to enhance the performance of OLEDs. In this paper, the PMS prepared by the phase separation of Polystyrene and Poly (methyl methacrylate) was integrated to the OLEDs with the structures of Glass/PMS/Ag (30 nm)/MoO₃ (5 nm)/(NPB) (40 nm)/(Alq₃) (60 nm)/LiF (0.5 nm)/Al (150 nm). The maximum luminance intensity and external quantum efficiency increased to 10700 cd/m² and 1.11 %, which is 48 % and 44 % higher than that of 7209 cd/m² and 0.77 % of the planar reference device. The enhanced performance of OLEDs was ascribed to the attenuation of surface plasmon polariton loss caused by the PMS, which was testified by the Finite-Difference Time-Domain (FDTD) simulation. The PMS was also transferred to the hole transfer layer (PEDOT: PSS) of OLEDs by nano-imprinting lithography with the structure of Glass/(ITO) (100 nm)/PEDOT: PSS (100 nm) (with PMS)/NPB (10 nm)/Alq₃ (50 nm)/LiF (0.5 nm)/Al (100 nm). The performance was also improved by the optimized PMS and the light out-coupling efficiency increased to about 49.5 %, which is much higher than that of 28.8 % in the OLEDs with PMS Ag anode and 20 % in the planar reference devices. This suggests that the PMS can improve the OLED device performance regardless of the functional layer in which the PMS is integrated.

Viaxl: A Solution of a Low-Cost Real-Time Visual Accelerometer Based on Laser Speckle Optical Flow Detection

Non-contact and non-destructive acceleration measurement is receiving considerable attention due to their low cost, flexibility, and simplicity of implementation, as well as their excellent performance in some emerging applications such as medical electronics applications, vibration monitoring, and some other special scenarios. In this paper, a visual accelerometer system based on laser speckle optical flow detection named Viaxl is proposed. Compared with the conventional non-contact acceleration measurement method based on a laser system, Viaxl has moderate and stable performance with the advantages of low cost and simplicity of implementation. Experiment results demonstrate that Viaxl, which consists of a commercial camera and a low-cost laser pointer, can achieve real-time, non-contact acceleration measurement, and confirm the basic system performance of Viaxl: a measurement nonlinearity better than 1.3%, up to 31 dB signal-to-noise ratio, and 1150 Hz theoretic bandwidth; this demonstrates the huge potential of Viaxl in a wide range of applications, and provides a new possible technical method for non-contact acceleration detection.

Polymer hybrid white quantum dots light-emitting diodes with a nanostructured electron injection layer

In this study, poly(N-vinylcarbazole) (PVK) polymer was blended with various dimensional CdSe/ZnS core-shell quantum dots to be used as a single emissive layer of white quantum dots light-emitting diodes (WQLEDs). Besides, the nanostructured ITO/ZnO nanorod array was used as electron transport/injection layer to shorten carrier transport distance, accelerate carrier transport velocity, and enhance carrier transport surface area. Consequently, luminance and luminous efficiency were increased by the resulting increase of the carrier injection current density and the hole-electron recombination opportunity. The CIE of (0.329, 0.331) was obtained for the WQLEDs by using the weight ratio of 1.5:1.3:2.2 of the red, green, and blue (RGB) quantum dots. Compared with the WQLEDs without the nanorod array, the WQLEDs with the 1.5-µm-periodic ITO/ZnO nanorod array obtained an increased luminance of 16333 cd/m² (compared with 7191 cd/m²) and an increased luminous efficiency of 3.13 cd/A (compared with 2.30 cd/A).

Transparent and Water-Resistant Composites Prepared from Acrylic Resins ABPE-10 and Acetylated Nanofibrillated Cellulose as Flexible Organic Light-Emitting Device Substrate

Acetylated nanofibrillated cellulose (ANFC)/acrylic resin ABPE-10 composite film was prepared by impregnating ABPE-10 into ANFC films under negative pressure, which can enhance properties of ANFC films by forming an interpenetrating polymer network structure between ABPE-10 and the ANFC film. The ANFC/ABPE-10 composite film met the high performance flexible organic light-emitting diode substrate requirement, even when the ANFC dosage was as high as approximately 70%. The transparency of films with different ANFC dosages significantly increased from 67% (42 µm) to 88% (45 µm), as determined by ultraviolet-visible analysis. The composite film inherited the properties of AFNC, with a low coefficient of thermal expansion and a ductile compact structure. The contact angles of ANFC films increased from 49.2° to 102.9° after dipping in ABPE-10. Additionally, the composite films had good surface smoothness and mechanical properties.