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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Device model for intermediate band materials
摘要： Gallium nitride (GaN) is a wide bandgap semiconductor material and is the most popular material after silicon in the semiconductor industry. The prime movers behind this trend are LEDs, microwave, and more recently, power electronics. New areas of research also include spintronics and nanoribbon transistors, which leverage some of the unique properties of GaN. GaN has electron mobility comparable with silicon, but with a bandgap that is three times larger, making it an excellent candidate for high-power applications and high-temperature operation. The ability to form thin-AlGaN/GaN heterostructures, which exhibit the 2-D electron gas phenomenon leads to high-electron mobility transistors, which exhibit high Johnson’s figure of merit. Another interesting direction for GaN research, which is largely unexplored, is GaN-based micromechanical devices or GaN microelectromechanical systems (MEMS). To fully unlock the potential of GaN and realize new advanced all-GaN integrated circuits, it is essential to cointegrate passive devices (such as resonators and filters), sensors (such as temperature and gas sensors), and other more than Moore functional devices with GaN active electronics. Therefore, there is a growing interest in the use of GaN as a mechanical material. This paper reviews the electromechanical, thermal, acoustic, and piezoelectric properties of GaN, and describes the working principle of some of the reported high-performance GaN-based microelectromechanical components. It also provides an outlook for possible research directions in GaN MEMS.
关键词： wide bandgap,resonators,HEMT,micromachining,III-V,microelectromechanical systems,piezoelectric materials
更新于2025-09-16 10:30:52
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Perspective: Ga <sub/>2</sub> O <sub/>3</sub> for ultra-high power rectifiers and MOSFETS
摘要： Gallium oxide (Ga2O3) is emerging as a viable candidate for certain classes of power electronics with capabilities beyond existing technologies due to its large bandgap, controllable doping, and the availability of large diameter, relatively inexpensive substrates. These applications include power conditioning systems, including pulsed power for avionics and electric ships, solid-state drivers for heavy electric motors, and advanced power management and control electronics. Wide bandgap (WBG) power devices offer potential savings in both energy and cost. However, converters powered by WBG devices require innovation at all levels, entailing changes to system design, circuit architecture, qualification metrics, and even market models. The performance of high voltage rectifiers and enhancement-mode metal-oxide field effect transistors benefits from the larger critical electric field of β-Ga2O3 relative to either SiC or GaN. Reverse breakdown voltages of over 2 kV for β-Ga2O3 have been reported, either with or without edge termination and over 3 kV for a lateral field-plated Ga2O3 Schottky diode on sapphire. The metal-oxide-semiconductor field-effect transistors fabricated on Ga2O3 to date have predominantly been depletion (d-mode) devices, with a few demonstrations of enhancement (e-mode) operation. While these results are promising, what are the limitations of this technology and what needs to occur for it to play a role alongside the more mature SiC and GaN power device technologies? The low thermal conductivity might be mitigated by transferring devices to another substrate or thinning down the substrate and using a heatsink as well as top-side heat extraction. We give a perspective on the materials’ properties and physics of transport, thermal conduction, doping capabilities, and device design that summarizes the current limitations and future areas of development. A key requirement is continued interest from military electronics development agencies. The history of the power electronics device field has shown that new technologies appear roughly every 10-12 years, with a cycle of performance evolution and optimization. The older technologies, however, survive long into the marketplace, for various reasons. Ga2O3 may supplement SiC and GaN, but is not expected to replace them.
关键词： MOSFETs,β-Ga2O3,rectifiers,power electronics,thermal conductivity,Gallium oxide,Ga2O3,doping,wide bandgap semiconductors,military electronics
更新于2025-09-16 10:30:52
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Efficient sky-blue perovskite light-emitting diodes via photoluminescence enhancement
摘要： The efficiencies of green and red perovskite light-emitting diodes (PeLEDs) have been increased close to their theoretical upper limit, while the efficiency of blue PeLEDs is lagging far behind. Here we report enhancing the efficiency of sky-blue PeLEDs by overcoming a major hurdle of low photoluminescence quantum efficiency in wide-bandgap perovskites. Blending phenylethylammonium chloride into cesium lead halide perovskites yields a mixture of two-dimensional and three-dimensional perovskites, which enhances photoluminescence quantum efficiency from 1.1% to 19.8%. Adding yttrium (III) chloride into the mixture further enhances photoluminescence quantum efficiency to 49.7%. Yttrium is found to incorporate into the three-dimensional perovskite grain, while it is still rich at grain boundaries and surfaces. The yttrium on grain surface increases the bandgap of grain shell, which confines the charge carriers inside grains for efficient radiative recombination. Record efficiencies of 11.0% and 4.8% were obtained in sky-blue and blue PeLEDs, respectively.
关键词： radiative recombination,perovskite light-emitting diodes,yttrium (III) chloride,photoluminescence quantum efficiency,wide-bandgap perovskites
更新于2025-09-12 10:27:22
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Wide‐Bandgap Perovskite/Gallium Arsenide Tandem Solar Cells
摘要： Gallium arsenide (GaAs) photovoltaic (PV) cells have been widely investigated due to their merits such as thin-film feasibility, flexibility, and high efficiency. To further increase their performance, a wider bandgap PV structure such as indium gallium phosphide (InGaP) has been integrated in two-terminal (2T) tandem configuration. However, it increases the overall fabrication cost, complicated tunnel-junction diode connecting subcells are inevitable, and materials are limited by lattice matching. Here, high-efficiency and stable wide-bandgap perovskite PVs having comparable bandgap to InGaP (1.8–1.9 eV) are developed, which can be stable low-cost add-on layers to further enhance the performance of GaAs PVs as tandem configurations by showing an efficiency improvement from 21.68% to 24.27% (2T configuration) and 25.19% (4T configuration). This approach is also feasible for thin-film GaAs PV, essential to reduce its fabrication cost for commercialization, with performance increasing from 21.85% to 24.32% and superior flexibility (1000 times bending) in a tandem configuration. Additionally, potential routes to over 30% stable perovskite/GaAs tandems, comparable to InGaP/GaAs with lower cost, are considered. This work can be an initial step to reach the objective of improving the usability of GaAs PV technology with enhanced performance for applications for which lightness and flexibility are crucial, without a significant additional cost increase.
关键词： gallium arsenide,phase segregation,perovskite/GaAs tandem cells,thin-film flexible tandem cells,wide-bandgap perovskites
更新于2025-09-12 10:27:22
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Understanding of Imine Substitution in Wide Bandgap Polymer Donor–Induced Efficiency Enhancement in All-Polymer Solar Cells
摘要： All-polymer solar cells (all-PSCs) are proven to possess outstanding thermal and mechanical stabilities. However, concurrently achieving appropriate phase-separated pattern, efficient charge transportation, and adequate charge transfer between donor and acceptor components is still a challenge, and thus, only a few polymer-polymer BHJ blends have yielded BHJ device PCEs >8%. Generally, polymer backbone substitutions may have a direct influence on the device performance. Thus, this report examines a set of wide bandgap polymer donor analogues composed of thienothiophene (TT) or thiazolothiazole (TTz) motif, and their all-PSC device performance with N2200. Results show that all-PSCs based on the imine-substituted derivative PBDT-TTz exhibit power conversion efficiencies (PCE) as high as 8.4%, which largely outperform the analogue PBDT-TT-based ones with PCEs of only 0.7%. This work reveals that the imine substitution in polymer backbones of PBDT-TTz not only increases the ionization potential (IP) and electron affinity (EA), narrows the optical gap (Eopt), but also has significantly impacts on the BHJ film morphologies. PBDT-TTz:N2200 BHJ blends present better miscibility, suppressed phase separation, much stronger crystallinity, and face-on ordering, which are contributed to efficient exciton dissociation, charge transportation, and therefore, high-efficiency in all-PSCs. This study demonstrates that the imine-substituted polymers composed of TTz motif, which can be easily synthesized through a facile two-step procedure, are a promising class of wide bandgap polymer donors for efficient all-PSCs.
关键词： Imine substitution,All-polymer solar cells,Thiazolothiazole,Wide bandgap polymer donors,BHJ film morphologies
更新于2025-09-12 10:27:22
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Universal host materials based on carbazole-formate derivatives for blue, green and red phosphorescent organic light-emitting diodes
摘要： The design of universal hosts suitable for different color dopants is still desired for efficient organic light-emitting diodes (OLEDs). In this work, two novel carbazole-formate based isomers (2CzMC and 4CzMC) with planar donor?π?acceptor (D?π?A) structures were designed and synthesized as the hosts for phosphorescent OLEDs (PhOLEDs). Due to the weak intramolecular charge transfer character and limited conjugation extensions, both 2CzMC and 4CzMC showed wide-bandgap emissions around 380 nm and high triplet energy levels (2.83 eV for 2CzMC, and 2.90 eV for 4CzMC). The photoluminescent spectra of 2CzMC and 4CzMC doped films with blue, green and red phosphors exhibited completely energy transfer from the hosts to the dopants. PhOLEDs devices with similar structures employing these doped film as emitter layers achieved excellent performance. Especially for 4CzMC-FIrpic based blue device, the external quantum efficiency (EQE) reached as high as 18.9%. This study showed a molecular design strategy to develop novel carbazole-based hosts for different color PhOLEDs.
关键词： Phosphorescent Organic Light-Emitting Diodes (PhOLEDs),Host,Carbazole,Wide-bandgap,Formate
更新于2025-09-12 10:27:22
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Micro tuning of wide-bandgap perovskite lattice plane for efficient and robust high-voltage planar solar cells exceeding 1.5 V
摘要： Iodide-free tribromide based perovskites, with their wide bandgap of over 2.0 eV, are highly regarded as potential candidates for a photoelectrochemical water splitting system and the topmost cell in tandem solar cell. Herein, we report on the importance of micro tuning of crystal-lattice by cesium incorporation into A-site on low temperature processed formamidinium lead tribromide (CH(NH2)2PbBr3 = FAPbBr3) perovskite films. The partial incorporation of cesium bromide (CsBr) in to FAPbBr3 film tunes crystal-lattice interactions, resulting in a high-purity cubic crystal system with preferred orientation. An entirely low temperature processed planar photovoltaic device assembled with FAPbBr3 containing 8% Cs (Cs0.08FA0.92PbBr3) exhibited an optimum PCE (power conversion efficiency) of 8.56% with a Voc (open-circuit voltage) of 1.516 V, which is higher than the PCE of 7.07% and Voc of 1.428 V of the FAPbBr3 device. Photoluminescence-intensity and temporal-imaging measurements were conducted by laser scanning confocal time-resolved microscopy (LCTM), which revealed that CsBr incorporation into a FAPbBr3 film significantly suppresses the non-radiative recombination pathways and homogenizes the spatial distribution of photoluminescence. It was visualized that the incorporation of CsBr in FAPbBr3 directly affects the bulk defect and photoluminescence properties, which provides evidence that Cs ions surely alleviate the segregation and aggregation of ions in the perovskite film. Notably, the Cs0.08FA0.92PbBr3 film, with a carrier lifetime of about 270 ns, exhibited a 1.37-fold longer radiative recombination time than that (210 ns) observed for the FAPbBr3 film. Furthermore, aging experiments without encapsulation under ambient (in air for 2000 h) and severe (65 °C and 65% RH for 500 h) conditions revealed that the Cs0.08FA0.92PbBr3 devices were more robust than the FAPbBr3 devices.
关键词： Low-temperature process,High-photovoltage,Wide-bandgap,CsBr,FAPbBr3
更新于2025-09-12 10:27:22
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Overview of Recent Progress of Semiconductor Power Devices based on Wide Bandgap Materials
摘要： Wide bandgap materials, which have shown superior material properties, such as better thermal conductivity and excellent electric performance, have aroused wide concern from scientists and engineers. Currently, research towards semiconductor power devices based on wide bandgap materials has made great achievements. The new developed WBG (wide bandgap) power devices, such as 1200V Direct-Driven SiC JFET power switch and highly reliable GaN MOS HFET displayed better performances and advantages, comparing to traditional Si based power devices. These power devices have been widely used in variety of applications with its successful commercialization, which convincingly proved their reliability and effectiveness. The usage of WBG power devices greatly improved the circuit performance, contributed to the evolve of the new generation electric products. In this paper, we mainly focus on introducing recent progresses and research results of several type of power devices based on WBG materials, including GaN, IGBT, JFET, MOSFET, rectifiers and their SiC counterparts. Their characteristics, performances and relevant applications will be discussed and compared respectively. Then, some deficiency and limits of these devices, as well as solutions of these defects will be illustrated. Finally, future developments and prospects of WBG power devices will be analyzed.
关键词： rectifiers,GaN,IGBT,MOSFET,wide bandgap materials,SiC,JFET,semiconductor power devices
更新于2025-09-11 14:15:04
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[IEEE 2018 International Power Electronics Conference (IPEC-Niigata 2018 –ECCE Asia) - Niigata, Japan (2018.5.20-2018.5.24)] 2018 International Power Electronics Conference (IPEC-Niigata 2018 -ECCE Asia) - Modeling and model parameter extraction of wide bandgap power semiconductor device, package, and circuit for simulating fast switching behavior
摘要： Wide band gap power semiconductor devices have superiority in fast switching operation, when compared to Si IGBT and PiN diodes for voltage range from several hundred to several kilo volts. The fast switching operation gives high di/dt and dv/dt, which results in inducing surge voltage and EMI noise for poorly designed circuit. The precise dynamical model of power device and peripheral component is necessary in estimating these transient phenomenon. This paper presents the dynamical model of wide bandgap power semiconductor devices, package of power device, and circuit wiring. The fixture configurations to extract model parameter is also presented. The static blocking and conducting condition for power device is characterized with curve tracer. The terminal capacitance of power device dominates switching dynamic terminal characteristics. Then, voltage dependency of capacitances are characterized with the developed fixture, which can cope with normally on transistor characterization. The electro magnetic analysis of package and circuit to identify parasitic component is also addressed in the paper. The switching behaviors of power device and the phenomenon in the circuit are discussed based on the model and extracted model parameters.
关键词： parameter extraction,wide bandgap power semiconductor devices,modeling,fast switching behavior,simulation
更新于2025-09-10 09:29:36
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Gallium Oxide || Schottky contacts to β-Ga2O3
摘要： The success of β-Ga2O3 as the wide-bandgap semiconductor platform for ultrahigh efficiency electronic and optoelectronic devices relies on the ability to control the properties of ohmic and rectifying, or Schottky, contacts on this material. This chapter focuses on the current status of research and development of Schottky contacts on β-Ga2O3: the materials and structures used and their corresponding electrical properties.
关键词： Schottky contacts,β-Ga2O3,electronic devices,optoelectronic devices,wide-bandgap semiconductor
更新于2025-09-10 09:29:36