In order to explore the relationship between the highest occupied molecular orbital (HOMO) energy level of hole transport materials (HTM) and the performance of organic light-emitting devices (OLEDs), nine HTMs based on the triphenylamine framework were studied. It is determined through experimental and simulation methods that the device performance is optimized when the HOMO energy level is within the range of -5.40 eV to -5.45 eV. The impedance characteristics of OLEDs also verify that with the increase in the HOMO energy level, the hole injection mechanism gradually shifts from tunneling injection to thermionic emission injection. This study serves as a valuable reference and inspiration for optimizing material matching in OLEDs, thus contributing to the further development of OLED technology.
Quantum dots (QDs) is widely used in the display field due to its excellent photoelectric properties and relatively good stability. The patterning of QD is an important part of solid state integration of high precision QDs optoelectronic devices. However, traditional patterning techniques either degrade material properties or have complex processes. In this study, selective electrophoretic deposition (SEPD) was used as a patterning strategy, and polymer additives were added to the QD ink to improve the deposition morphology and achieve efficient and non-destructive patterning.
Perovskite quantum dot light-emitting diodes (PeQLEDs) have emerged as a promising candidate for high-quality lighting and displays, where significant progress has been made in the modification and optimization of perovskite quantum dots (PeQDs) emitting layer to achieve improved device efficiency. However, limited attention has been given to interfacial trap state passivation for efficient and stable PeQLEDs thus far. We propose a straightforward approach to enhance the performance of PeQLEDs by thermal-evaporating a phosphine oxide molecule, SPPO13, onto the PeQDs emitting layer as an interface passivation layer. The interfacial passivation leads to a significant improvement in both maximum brightness and maximum external quantum efficiency (EQE) of PeQLEDs, reaching 28907.1 cd m-2 and 10.3%, respectively. This enhancement is attributed to reduced trap-assisted recombination and improved electron transport characteristics.
This article presents a novel voltage-programmed pixel circuit using a-IGZO TFTs to effectively compensate threshold voltage (Vth) variations of driving TFT. The compensation is very important to maintain the pixel brightness of active matrix organic light-emitting diodes (AMOLED) displays. The proposed pixel design uses four-phase clocking schemes: initial period, compensation period (Vth detection), data input period and emission period. To maintain uniformity in phases, the duration of all the phases is taken to be same which results in easier design of the multi-phase clock. Moreover, the circuit has been extensively simulated with control signal and the operation has been verified using SPICE from Aether EDA. The key of this paper is changing the compensation timing of the pixel circuit, which can greatly broaden the Vth compensation range of the driving TFT from -0.30~0.30 to -0.85~1.45V by means of simulation.
A 32×32 pixel avalanche photodiode array read-out circuit is presented. The pixel structure adopts a specially designed active-quenching circuit along with function of self-check, auto-reset, and high-voltage protection. The chip is expected to be used with Avalanche Photodiode (APD) array working at Geiger Mode, and the data of each pixel can be serially output individually in 32 channels. The chip has been fabricated in a 0.18um standard CMOS technology. The pixel pitch is 100um, while the whole chip size is 5 × 6 mm2 which has realized low quenching time of 1ns, high-voltage protection (60V), and minimum time resolution of 500ps.
Liquid crystal materials don’t emit light, and its phase difference is connections with viewing angle. In general, the brightness of liquid crystal displays (LCD) is limited and the color shift apparently exists at large viewing angles. Furthermore, the same problem is also emerged in organic light emitting diode (OLED) displays. Microcavity resonance effect in OLED seriously affects the luminance and brings about “blue shift” as viewing angle increases. We propose an optical film with micro-prism to improve the viewing angle characteristics of LCD and OLED, which can increase the brightness and decrease the color shift. Excellent agreements supported by simulations and experiments are obtained. The proposed optical film is coated on a 75in. 8K (7680×4320) LCD to measure the optical parameters. When the viewing (polar) angle is between ±60° and a white pattern is displayed, the maximum color shift Δμ'v' can be decreased from 0.027 to 0.006 after the proposed optical film is introduced. Moreover, the brightness at large viewing angles is enhanced obviously, both theoretical and experimental results are proved that the luminance is about 5%~40% higher than previous when the viewing angle ranges from 30° to 60° correspondingly.
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