Working Mechanisms of Nanoscale Light-Emitting Diodes Operating in Non-Electrical Contact and Non-Carrier Injection Mode: Modeling and Simulation

Li, Wenhao; Wang, Kun; Li, Junlong; Wu, Chaoxing; Zhang, Yongai; Zhou, Xiongtu; Guo, Tailiang

doi:10.3390/nano12060912

Cited by 19 publications

(9 citation statements)

References 40 publications

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“…Recently, micro-light-emitting diode has been emerging as a promising electronic platform for advanced applications, including ultrahigh resolution displays, visible light communications, and biocompatible lighting sources [ 1 , 2 , 3 ]. Different from conventional driving mode, noncarrier injection (NCI) mode has been demonstrated for using in micro–scale LED and nano-scale LED [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ]. As an electrical contact between the external electrodes and the LED chip is avoided, the device structure and manufacturing process can be simplified.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, under an external alternating current (AC) electric field, only the inherent electrons and holes contribute to the periodical radiative recombination. The electrical and optical properties of NCI–LEDs, including current-voltage properties, current-frequency properties, brightness-frequency properties, and light-pulse splitting etc., have been measured experimentally [ 4 , 5 , 6 , 7 , 8 , 9 ]. However, there is still a lack of theoretical model for NCI–LEDs, which is critical for designing a compatible NCI–LED for specific applications.…”

Section: Introductionmentioning

confidence: 99%

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Theoretical Study of LED Operating in Noncarrier Injection Mode

Wang

Guo

2022

Nanomaterials

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Non–carrier injection (NCI) mode is an emerging driving mode for light–emitting diodes (LEDs) with numerous advantages. Revealing the relationship between the current and the applied alternating voltage in mathematical formulas is of great significance for understanding the working mechanism of NCI–LEDs and improving device performance. In this work, a theoretical model of the relationship between NCI–LED current and time–varying voltage is constructed. Based on the theoretical model, the real–time current is derived, which is consistent with the experimental results. Key parameters that can improve device performance are discussed, including voltage amplitude, frequency, equivalent capacitance, and LED reverse current. The theory presented here can serve as an important guidance for the rational design of the NCI–LEDs.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Theoretical Study of LED Operating in Noncarrier Injection Mode

Wang

Guo

2022

Nanomaterials

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“…[ 1–3 ] For example, the opposites of the north and south poles allow the use of a compass to determine direction, [ 4 ] and the utilization of concave and convex prisms leads to the construction of various optical systems. [ 5 ] Furthermore, because of the existence of electrons and holes, semiconductors have become the base blocks of optoelectronic devices, [ 6,7 ] with metal‐oxide‐semiconductor field effect transistors (MOSFETs) having the opposites of p‐type and n‐type channels and the ability to achieve the basic functions of complementary metal‐oxide‐semiconductor (CMOS) transistors ( Figure a). [ 8 ] As for neuromorphic science, the realization of complementary behaviors is also important because two complementary behaviors are seen to exist in neuroglia: 1) astrocytes can significantly increase the number of neuronal synapses, [ 9,10 ] and 2) microglia can engulf synapses and cause a decrease in the number of synapses in engram cells.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic Equilibrium‐Nonequilibrium Competition in Nanofilaments for Achieving Complementary Electronic Synapses

Guo

Liao

et al. 2022

Adv Funct Materials

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In the human brain, the natural complementary behaviors of synapse connections, which are enhanced and weakened through the participation of astrocytes and microglias, play an important role in the process of training and memory. Even though memristors based on the electrochemical metallization mechanism (ECM) have great potential in realizing electronic synapses (e‐synapses), the lack of complementary ECM e‐synapses has, to a certain extent, hindered the construction of artificial neural networks. In this study, the thermodynamic equilibrium‐nonequilibrium competition (TC) in nanofilaments is meticulously designed by modifying the metal‐ion nanochannels to achieve complementary ECM e‐synapses. The evolution in the morphology of a TC‐induced nanofilament includes a thinning behavior of the nanofilaments caused by electrical stimulation and a coarsening behavior caused by metal‐ion chelation. The TC effect leads to a decrease in the conductance under positive pulse stimulation and to an increase in the conductance while resting, these behaviors being exactly complementary to those of a conventional ECM e‐synapse. Finally, the feasibility of fabricating logic gate circuits with learning capability based on complementary ECM e‐synapses is verified using behavioral‐level modeling. These ECM e‐synapses with complementary functions are expected to be significant to researchers in the field of large neural network systems.

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“…源矩阵驱动两种 [11,12] 。但无论是采用何种驱动方式，外电极与 LED 芯片必须要存在良好的电学接触以保证高效的载流子注入。因此，实现外延基板上的巨量微纳 LED 芯片与显示背板上驱动结构之间精准的空间对准以保证 LED 芯片与驱动电极形成良好的电气连接是核心关键技术之一 [13] 。由于微纳 LED 尺寸只有几百纳米到几十微米，且需要对准的 LED 芯片数量高达百万甚至上亿颗之多，要实现 LED 芯片与驱动电路的高性能电学接触也愈发困难，这成为阻碍微纳 LED 走向大规模商业化应用的瓶颈。另一方面，驱动电极与微纳 LED 之间不可避免地会有接触电阻并由此产生焦耳热，影响器件工作性能。虽然电极与微纳 LED 之间的界面处理能最大程度地消除接触电阻，但是随着 LED 尺寸缩小至亚微米，界面处理难度将显著加大，并有可能影响器件发光性能 [14][15][16] 。 2020 年福州大学郭太良、吴朝兴团队提出了一种交流驱动的无外部载流子注入微米 LED 器件与纳米 LED 器件(无注入型微纳 LED) ，即电极与 LED 芯片之间无电学接触无外部载流子注入 [17,18] 。该工作模式有望消除接触电阻带来的影响以及降低对金属键合的高精度要求。但是，有关无注入微纳 LED 的理论研究只是停留在对内部载流子输运的定量描述，并没有具体的物理和数学模型。由于传统 LED 复合发光的载流子来源于外部，现有的载流子输运模型(即传统的 PN 结模型)无法直接应用于无注入型 LED。另一方面，无注入型 LED 器件由于隔绝了外部载流子的注入，将面临着发光效率低、驱动电压高和需要高频交流电等问题，急需用于器件优化的理论指导 [19]…”

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Carrier transport model of non-carrier-injection light-emitting diode

Jiancheng¹,

Wu²,

Guo³

2023

Acta Phys. Sin.

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Non-carrier-injection light-emitting diodes (NCI-LEDs) are expected to be widely used in next generation micro-display technologies, including Micro-LEDs and nano-pixel light-emitting displays due to their simple device structure. However, because there is no charge carrier injection from external electrodes, carrier transport behavior of the NCI-LED cannot be described by using the traditional PN junction and LED theory. Therefore, establishing a carrier-transport model for the NCI-LED is of great significance for understanding its working mechanism and for improving device performance. In this paper, carrier transport mathematical model of the NCI-LED is established and the mechanical behavior of charge-carrier transport is analyzed quantitatively. Based on the mathematical model, the working mechanism of the NCI-LED is explained, the carrier transport characteristics of the device are obtained. Additionally, the key features, including the length of the induced charge region, the forward biased voltage across the internal PN junction, and the reverse biased voltage across the internal PN junction are studied. Their relationships with the applied frequency of the applied driving voltage are revealed. It is found that both the forward and reverse biases of the internal PN junction increase with the driving frequency. When the driving frequency reaches a certain value, the forward and reverse bias of the PN junction would be maintained at a maximum value. Moreover, the length of the induced charge region decreases with the increase of the driving frequency, and when the frequency reaches a certain value, the induced charge region would always be in the state of exhaustion. According to the mathematical model, suggestions for the device optimization design are provided: (1) Reducing the doping concentration of the induced charge regions can effectively increase the voltage drop across the internal LED; (2) Employing the tunneling effect occurring in the reverse-biased PN junction can effectively improve the electroluminescence intensity; (3) Using square-wave driving voltage can obtain a larger voltage drop across the internal LED and increase the electroluminescence intensity. This work on the carrier transport model is expected to provide a clear physical image for understanding the working mechanism of NCI-LED, and to provide a theoretical guidance for optimizing the device structure.

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Working Mechanisms of Nanoscale Light-Emitting Diodes Operating in Non-Electrical Contact and Non-Carrier Injection Mode: Modeling and Simulation

Cited by 19 publications

References 40 publications

Theoretical Study of LED Operating in Noncarrier Injection Mode

Theoretical Study of LED Operating in Noncarrier Injection Mode

Thermodynamic Equilibrium‐Nonequilibrium Competition in Nanofilaments for Achieving Complementary Electronic Synapses

Carrier transport model of non-carrier-injection light-emitting diode

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