A Comparative Study of GaN‐Based Direct Current and Alternating Current High Voltage Light‐Emitting Diodes

Abstract

In this work, one type of direct current high voltage light‐emitting diode (DC‐HV LED) and six types of alternating current high voltage LEDs (AC‐HV LEDs) are demonstrated. Comparative current‐voltage (I–V) and light output power (LOP)‐current (L‐I) characteristics are performed between 24 V DC‐HV LED and 24 V AC‐HV LEDs with eight working cells. The AC‐HV LED has relatively larger wall‐plug efficiency (WPE) than DC‐HV LED over a current density range from 0 to 152 A cm−2. The effect of the layouts on the optical and electrical properties of AC‐HV LEDs is further investigated. Owing to larger heat dissipation area and fewer number of chips, our combined numerical and experimental results demonstrate that the AC‐HV LED I has a more favorable current spreading uniformity compared to other AC‐HV LEDs. In addition, it is found that the LOP of AC‐HV LEDs is dependent on both the number of working cells and the ratio of radiation area to total chip area. Larger ratio of light emission area to total chip area can be obtained by decreasing the area of rectifier cells. Therefore, in order to achieve a much higher LOP, AC‐HV LEDs have to be designed with smaller area of rectifier cells and with more working cells simultaneously.

Over 700 MHz –3 dB Bandwidth UOWC System Based on Blue HV-LED With T-Bridge Pre-Equalizer

“…Dividing a large area LED chip into numerous serially connected LED cells improved the brightness of GaN-based LEDs and at the same time avoided the poor current spreading problem [21]. HV-LEDs can provide large optical power in small size (over 350 mW in a size of 896 μm × 432 μm, as reported in [22]). Single-chip highvoltage LEDs also enable simplified driver design, because its operation voltage is closer to mains or DC voltage supplies [23].…”

Recent Progress in AC-Driven Organic and Perovskite Electroluminescent Devices

“…That is because the strong electric field will lead to a harmful halide migration and the present chlorine-rich and bromine-rich areas in the perovskite film, resulting in phase separation and a red shift of the EL spectrum . Therefore, it is a promising method for the achievement of blue PeLEDs with a stable spectrum through electrical regulation. , Tan et al first demonstrated pure blue PeLEDs with a stable spectrum, driven by a square wave AC voltage . As shown in Figure d, the authors built the PeLEDs with the structure of ITO/PEDOT:PSS/perovskite/TPBi/LiF/Al.…”

“…119 Therefore, it is a promising method for the achievement of blue PeLEDs with a stable spectrum through electrical regulation. 120,121 Tan et al first demonstrated pure blue PeLEDs with a stable spectrum, driven by a square wave AC voltage. 122 As shown in Figure 13d, the authors built the PeLEDs with the structure of ITO/ PEDOT:PSS/perovskite/TPBi/LiF/Al.…”

AC-driven multicolor electroluminescence from a hybrid WSe2 monolayer/AlGaInP quantum well light-emitting device

“…Some of the latest research has demonstrated that gallium nitride (GaN)-based LEDs can be operated without an AC-DC converter being required, revealing their potential for application in energyefficient and reliable LED lighting systems. [51][52][53][54][55][56] Although ACdriven TMDC monolayer LEDs have been demonstrated recently, it is worth noting that several important issues, such as device upscaling difficulty and a small emission area, still remain unresolved at the current stage.…”