Design of an AC Driving Waveform Based on Characteristics of Electrowetting Stability for Electrowetting Displays

In traditional electrowetting display (EWD) drivers, direct current (DC) voltage and pulse width modulation are often used, which easily caused an electrowetting charge trapping phenomenon in a hydrophobic insulating layer. Therefore, the driving voltage must be increased for driving EWDs, and oil backflow cannot be solved. Aqueous solutions are often used as polar liquids for EWDs, and the reverse voltage of alternating current (AC) driving can cause chemical reactions between water and indium tin oxide (ITO). So, a driving waveform was proposed, which included a DC waveform and an AC waveform, to separately drive EWDs for oil rupture and open state. Firstly, a DC waveform was used when the oil was broken, and the response time was reduced by designing the DC voltage and duration. Secondly, an AC waveform was used when the oil required to be stable. Oil backflow could be suppressed by the AC waveform. The main parameters of AC waveform include reverse voltage, frequency and duty cycle. The reverse voltage of EWDs could be obtained by voltammetry. The frequency could be obtained by analyzing the rising and falling edges of the capacitance voltage curve. The experimental results showed that the proposed waveform can effectively suppress oil backflow and shorten the response time. The response time was about 86% lower than the conventional driving waveforms, and oil backflow was about 72% slower than the DC driving waveform.

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Line of Sight Correction of High-Speed Liquid Crystal Using Overdriving Technology

Electronics ◽

10.3390/electronics9091477 ◽

2020 ◽

Vol 9 (9) ◽

pp. 1477

Author(s):

Hongyang Guo ◽

Qing Li ◽

Yangjie Xu ◽

Yongmei Huang ◽

Shengping Du

Keyword(s):

Liquid Crystal ◽

Response Time ◽

High Speed ◽

Pulse Width Modulation ◽

Response Speed ◽

Line Of Sight ◽

Processing Unit ◽

Driving Voltage ◽

Light Modulator ◽

Central Processing

In the line of sight correction system, the response time of the liquid crystal spatial light modulator under the normal driving voltage is too long to affect system performance. On the issues, an overdriving method based on a Field-Programmable Gate Array (FPGA) is established. The principle of the overdrive is to use a higher voltage difference to achieve a faster response speed of liquid crystal. In this scheme, the overdriving look-up table is used to seek the response time of the quantized phase, and the liquid crystal electrode is driven by Pulse–Width Modulation (PWM). All the processes are performed in FPGA, which releases the central processing unit (CPU) memory and responds faster. Adequate simulations and experiments are introduced to demonstrate the proposed method. The overdriving experiment shows that the rising response time is reduced from 530 ms to 34 ms, and the falling time is from 360 ms to 38 ms under the overdriving voltage. Typical light tracks are imitated to evaluate the performance of the line of sight correction platform. Results show that using the overdrive the −3 dB rejection frequency was increased from 1.1 Hz to 2.6 Hz. The suppression ability of the overdrive is about −20 dB at 0.1 Hz, however the normal-driving suppression ability is only about −13 dB.

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Aperture Ratio Improvement by Optimizing the Voltage Slope and Reverse Pulse in the Driving Waveform for Electrowetting Displays

Micromachines ◽

10.3390/mi10120862 ◽

2019 ◽

Vol 10 (12) ◽

pp. 862 ◽

Cited By ~ 4

Author(s):

Zichuan Yi ◽

Wenyong Feng ◽

Li Wang ◽

Liming Liu ◽

Yue Lin ◽

...

Keyword(s):

Inflection Point ◽

Charge Trapping ◽

Response Speed ◽

Driving Voltage ◽

Hysteresis Characteristic ◽

Aperture Ratio ◽

Dynamic Display ◽

Capacitance Voltage ◽

Reverse Pulse ◽

Driving Waveform

Electrowetting display (EWD) performance is severely affected by ink distribution and charge trapping in pixel cells. Therefore, a multi structural driving waveform is proposed for improving the aperture ratio of EWDs. In this paper, the hysteresis characteristic (capacitance–voltage, C-V) curve of the EWD pixel is tested and analyzed for obtaining the driving voltage value at the inflection point of the driving waveform. In the composition of driving waveform, a voltage slope is designed for preventing ink dispersion and a reverse pulse is designed for releasing the trapped charge which is caused by hysteresis characteristic. Finally, the frequency and the duty cycle of the driving waveform are optimized for the max aperture ratio by a series of testing. The experimental results show that the proposed driving waveform can improve the ink dispersion behavior, and the aperture ratio of the EWD is about 8% higher than the conventional driving waveform. At the same time, the response speed of the driving waveform can satisfy the dynamic display in EWDs, which provides a new idea for the design of the EWD driving scheme.

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Design of Driving Waveform Based on Overdriving Voltage for Shortening Response Time in Electrowetting Displays

Frontiers in Physics ◽

10.3389/fphy.2021.642682 ◽

2021 ◽

Vol 9 ◽

Author(s):

Wenjun Zeng ◽

Zichuan Yi ◽

Yiming Zhao ◽

Weibo Zeng ◽

Simin Ma ◽

...

Keyword(s):

Response Time ◽

Physical Model ◽

Performance Testing ◽

Charge Trapping ◽

Response Speed ◽

Fast Response ◽

Optimal Performance ◽

Experimental Results ◽

Target Luminance ◽

Driving Waveform

A fast response speed of a pixel is important for electrowetting displays (EWDs). However, traditional driving waveforms of EWDs have the disadvantage of long response time. So, a driving waveform, which based on overdriving voltages and charge trapping theory, was proposed in this paper to shorten the response time of EWDs. The driving waveform was composed of an overdriving stage and a driving stage. Firstly, a simplified physical model was introduced to analyze the influence of driving voltages on the response time. Then, an overdriving voltage was applied in the overdriving stage to increase the respond speed of oil, and a target voltage was applied in the driving stage to obtain a target luminance. In addition, the effect of different overdriving voltages and overdriving time values on the response time was analyzed by charge trapping theory to achieve an optimal performance. Finally, the driving waveform was imported into an EWD for performance testing. Experimental results showed that the response time of the EWD can be shortened by 29.27% compared with a PWM driving waveform.

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A Combined Pulse Driving Waveform With Rising Gradient for Improving the Aperture Ratio of Electrowetting Displays

Frontiers in Physics ◽

10.3389/fphy.2021.709151 ◽

2021 ◽

Vol 9 ◽

Author(s):

Lixia Tian ◽

Pengfei Bai

Keyword(s):

Charge Trapping ◽

Fast Response ◽

Driving Voltage ◽

Film Rupture ◽

Aperture Ratio ◽

Full Color ◽

Display Technology ◽

Display Performance ◽

The Stability ◽

Driving Waveform

As a reflective display technology, electrowetting displays (EWDs) have the advantages of paper-like display, low power consumption, fast response, and full color, but the aperture ratio of EWDs is seriously affected by oil dispersion and charge trapping. In order to improve the aperture ratio and optimize the display performance of EWDs, a combined pulse driving waveform with rising gradient design was proposed. First, an initial driving voltage was established by the threshold voltage of oil film rupture (Vth). And then, a rising gradient was designed to prevent oil from dispersing. At last, the oil splitting and movement were controlled to achieve the target aperture combined with the pulse waveform. Experimental results showed that the oil dispersion of EWDs can be effectively improved by using the proposed driving waveform, the aperture ratio of EWDs was increased by 3.16%, and the stability was increased by 71.43%.

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Driving Waveform Design of Electrowetting Displays Based on a Reset Signal for Suppressing Charge Trapping Effect

Frontiers in Physics ◽

10.3389/fphy.2021.672541 ◽

2021 ◽

Vol 9 ◽

Author(s):

Taiyuan Zhang ◽

Yong Deng

Keyword(s):

Charge Trapping ◽

Recovery Phase ◽

Driving Voltage ◽

Aperture Ratio ◽

Trapping Effect ◽

Display Performance ◽

Reset Signal ◽

A Charge ◽

Driving Waveform ◽

Driving Signal

Electrowetting display (EWD) device is a new type of reflective optoelectronic equipment with paper-like display performance. Due to the oil backflow phenomenon, it is difficult for pixels to be maintained a stable aperture ratio, so the grayscale of EWDs cannot be stabilized. To reduce the oil backflow in EWDs, a driving waveform composed of a driving signal and a periodic reset signal was proposed in this paper. A direct current (DC) signal was designed as the driving signal for driving pixels. The aperture ratio of pixels was determined by the amplitude of the DC signal. The periodic reset signal was divided into a charge release phase and a driving recovery phase. During the charge release phase, the driving voltage was abruptly dropped to 0 V for a period to release trapped charges. In the driving recovery phase, the driving voltage was rapidly increased from 0 V to a maximum value. To reach the same grayscale of EWDs, the driving waveform was returned to the driving signal at the end of the driving recovery phase. Experimental results showed that the aperture ratio of EWDs was unchanged when the driving waveform was applied. However, the aperture ratio of pixels was gradually decreased with the conventional driving waveform. It was indicated that the charge trapping effect and the oil backflow phenomenon can be effectively inhibited by the proposed driving waveform. Compared with the conventional driving waveform, the speed of oil backflow was reduced by 90.4%. The results demonstrated that the proposed driving waveform is beneficial for the achievement of stable grayscale in EWDs.

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Dielectric Breakdown and Failure of Ferroelectric Films as the Dielectric for Electrowetting Systems

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.697.231 ◽

2016 ◽

Vol 697 ◽

pp. 231-234 ◽

Cited By ~ 2

Author(s):

Wei Qiang Wang ◽

Jia Qi Niu ◽

Zhen Kun Xie ◽

Zhen Xing Yue

Keyword(s):

Breakdown Voltage ◽

Dielectric Breakdown ◽

Breakdown Strength ◽

Charge Trapping ◽

Ferroelectric Thin Film ◽

Ferroelectric Film ◽

Dc Voltage ◽

Voltage Polarity ◽

Ferroelectric Layer ◽

Voltage Frequency

In this paper, we study the electrical properties and breakdown phenomena of PZT ferroelectric thin film in electrowetting systems. The experimental results indicate that irreversible charge trapping occurred with repeated voltage actuation, resulting in contact angle relaxation and reduction of the ferroelectric film breakdown strength. The breakdown voltage depends on DC voltage polarity, and this polarity dependence was found to be related to the thickness of the ferroelectric layer. When AC voltage was applied, the breakdown voltage increased directly with voltage frequency. These phenomena are interpreted in terms of electrochemical reactions at the liquid/solid interface, an empirical model was used to estimate the amount of trapped charge in the ferroelectric film.

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Dual-Cation Electrolytes Crosslinked with MXene for High-Performance Electrochromic Devices

Nanomaterials ◽

10.3390/nano11040874 ◽

2021 ◽

Vol 11 (4) ◽

pp. 874

Author(s):

Soyoung Bae ◽

Youngno Kim ◽

Jeong Min Kim ◽

Jung Hyun Kim

Keyword(s):

Ionic Conductivity ◽

Response Time ◽

Indium Tin Oxide ◽

High Performance ◽

Fast Response ◽

High Ionic Conductivity ◽

Electrochromic Device ◽

Fast Response Time ◽

Coloration Efficiency ◽

Conduction Pathway

MXene, a 2D material, is used as a filler to manufacture polymer electrolytes with high ionic conductivity because of its unique sheet shape, large specific surface area and high aspect ratio. Because MXene has numerous -OH groups on its surface, it can cause dehydration and condensation reactions with poly(4-styrenesulfonic acid) (PSSA) and consequently create pathways for the conduction of cations. The movement of Grotthuss-type hydrogen ions along the cation-conduction pathway is promoted and a high ionic conductivity can be obtained. In addition, when electrolytes composed of a conventional acid or metal salt alone is applied to an electrochromic device (ECD), it does not bring out fast response time, high coloration efficiency and transmittance contrast simultaneously. Therefore, dual-cation electrolytes are designed for high-performance ECDs. Bis(trifluoromethylsulfonyl)amine lithium salt (LiTFSI) was used as a source of lithium ions and PSSA crosslinked with MXene was used as a source of protons. Dual-Cation electrolytes crosslinked with MXene was applied to an indium tin oxide-free, all-solution-processable ECD. The effect of applying the electrolyte to the device was verified in terms of response time, coloration efficiency and transmittance contrast. The ECD with a size of 5 × 5 cm2 showed a high transmittance contrast of 66.7%, fast response time (8 s/15 s) and high coloration efficiency of 340.6 cm2/C.

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Rare Earth Ion Implantation for Silicon Based Light Emission

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.108-109.755 ◽

2005 ◽

Vol 108-109 ◽

pp. 755-760 ◽

Cited By ~ 7

Author(s):

Wolfgang Skorupa ◽

J.M. Sun ◽

S. Prucnal ◽

L. Rebohle ◽

T. Gebel ◽

...

Keyword(s):

Rare Earth ◽

Ion Implantation ◽

Indium Tin Oxide ◽

Light Emission ◽

Charge Trapping ◽

Electrical Performance ◽

Rare Earth Ion ◽

Light Emitting ◽

Silicon Based ◽

Luminescent Centers

Using ion implantation different rare earth luminescent centers (Gd3+, Tb3+, Eu3+, Ce3+, Tm3+, Er3+) were formed in the silicon dioxide layer of a purpose-designed Metal Oxide Silicon (MOS) capacitor with advanced electrical performance, further called a MOS-light emitting device (MOSLED). Efficient electroluminescence was obtained for the wavelength range from UV to infrared with a transparent top electrode made of indium-tin oxide. Top values of the efficiency of 0.3 % corresponding to external quantum efficiencies distinctly above the percent range were reached. The electrical properties of these devices such as current-voltage and charge trapping characteristics, were also evaluated. Finally, application aspects to the field of biosensing will be shown.

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Evidence of Hysteresis in a New p-i-n-i-p-i-n Amorphous Silicon Device

MRS Proceedings ◽

10.1557/proc-467-943 ◽

1997 ◽

Vol 467 ◽

Author(s):

D. Caputo ◽

G. De Cesare ◽

F. Palma

Keyword(s):

Charge Trapping ◽

Bistable Behavior ◽

Novel Device ◽

Voltage Curve ◽

Current Voltage ◽

Recombination Processes ◽

Current Voltage Curve ◽

Numerical Device ◽

Silicon Device

ABSTRACTA novel device based on a-Si:H p+-i-n−-i-p−-i-n+ structure, showing a hysteresis in its current-voltage curve is reported. A numerical device model allows to investigate in detail the fundamental role of the two lightly doped n− and p− layers, where charge trapping determines the bistable behavior of the device. The ON condition is mantained until the ambipolar charge injection overcomes the fixed charge. The transition OFF-ON starts when, increasing the applied voltage, one of the two lightly doped layers becomes completely depleted. The transition ON-OFF is, instead, mainly dependent on the recombination processes occurring in the central doped layers. Devices with hysteresis around 2 V and tum-on voltage around 12 are presented.

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