Approaches for High-Efficiency III-V/Si Tandem Solar Cells

The Si tandem solar cells are very attractive for realizing high efficiency and low cost. This paper overviews current status of III-V/Si tandem solar cells including our results. The analytical results for efficiency potential of Si tandem solar cells and loss analysis of Si bottom cells as well as bandgap energy optimization of sub-cells are presented. The 2-junction and 3-junction Si tandem solar cells have potential efficiencies of 36% and 42%, respectively. ERE (external radiative efficiency) analysis for Si solar cells is analyzed in order to clarify properties of Si bottom solar cells. Properties of single-crystalline Si heterojunction solar cell fabricated in this study were analyzed. The current status of efficiencies of our Si bottom cell, upper III-V 2-junction solar cell and III-V/Si 3-junction tandem solar cell was shown to be 5.2% and 28.6% and 33.8%. Achievement of Jsc of 12 mA/cm2 for Si bottom cell is necessary to realize high-efficiency 3-junction Si tandem solar cells with an efficiency of more than 37%. In addition, this paper presents ERE analysis of III-V 2-junction upper solar cells for improving III-V/Si 3-junction tandem solar cells. Several ways to improve efficiency of III-V/Si 3-junction tandem solar cells by reducing non-radiative recombination, optical and resistance losses are shown.

电动汽车的建模与模拟——不同锂离子电池技术的实施(英文)

受限制的续航距离是锂离子电池电动汽车的缺点之一。特别是在低温下,由于低的电池容量、功率,以及辅助设备的附带能量需求,使得该续航距离又被减少。选用了一种基于模型的方法,来比较几种不同的电池技术的车内性能。设定了不同的试验情景,分析电池特性。模拟结果表明:由于电池容量的减少,限制了制动器能量的恢复,因此,在城市近郊及低温环境下,动力系的能量需求明显升高。此外,针对不同的温度、电池尺寸和驾驶周期,分析了电池和动力系的效率。最后,针对不同驾驶周期、温度和附加载荷,研究了电动续航距离。

Study of large area hydrogenated microcrystalline silicon p-layers for back surface field in crystalline silicon solar cells

A series of hydrogenated microcrystalline silicon (μc-Si:H) p-layers for back surface field in crystalline silicon solar cells were deposited on glass substrates by the developed large area (45 cm×45 cm) plasma enhanced chemical vapour deposition processor operating at 13.56 MHz and various values of source gas trimethylboron (TMB) to H2 flowratio. The influence of deposition parameters on the large area p-layer performance was intensively studied,as well as the thin film uniformity,optical,electrical and structural performances by Raman,FTIR,Ellipsometry,etc. Arrhenius and Tauc plots were used to discuss the μc-Si:H thin film’s activation energy and the defects state distribution. When amorphous-microcrystalline transition state was obtained,the deposited p-doped μc-Si:H layers showed specific resistance of 38.3 Ω-1cm-1 at the flowratio of 0.66% and high crystallinity of 45%–50% with no further treatment. The effect of source gas flowratio,deposition rate,and source gas partial pressure on μc-Si:H thin film’s performance was also investigated.

Online Process Control of Alkaline Texturing Baths: Determination of the Chemical Concentrations

Almost every monocrystalline silicon solar cell design includes a wet chemical process step for the alkaline texturing of the wafer surface in order to reduce the reflection of the front side. The alkaline texturing solution contains hydroxide, an organic additive usually 2-propanol and as a reaction product silicate. The hydroxide is consumed due to the reaction whereas 2-propanol evaporates during the process. Therefore, the correct replenishment for both components is required in order to achieve constant processing conditions. This may be simplified by using analytical methods for controlling the main components of the alkaline bath. This study gives an overview for a successful analytical method of the main components of an alkaline texturing bath by titration, HPLC, surface tension and NIR spectrometry.

Fundamentals, materials, and machine learning of polymer electrolyte membrane fuel cell technology

Polymer electrolyte membrane(PEM)fuel cells are electrochemical devices that directly convert the chemical energy stored in fuel into electrical energy with a practical conversion efficiency as high as 65%.In the past years,significant progress has been made in PEM fuel cell commercialization.By 2019,there were over 19,000 fuel cell electric vehicles(FCEV)and 340 hydrogen refueling stations(HRF)in the U.S.(~8,000 and 44,respectively),Japan(~3,600 and 112,respectively),South Korea(~5,000 and 34,respectively),Europe(~2,500 and 140,respectively),and China(~110 and 12,respectively).Japan,South Korea,and China plan to build approximately 3,000 HRF stations by 2030.In 2019,Hyundai Nexo and Toyota Mirai accounted for approximately 63%and 32%of the total sales,with a driving range of 380 and 312 miles and a mile per gallon(MPGe)of 65 and 67,respectively.Fundamentals of PEM fuel cells play a crucial role in the technological advancement to improve fuel cell performance/durability and reduce cost.Several key aspects for fuel cell design,operational control,and material development,such as durability,electrocatalyst materials,water and thermal management,dynamic operation,and cold start,are briefly explained in this work.Machine learning and artificial intelligence(AI)have received increasing attention in material/energy development.This review also discusses their applications and potential in the development of fundamental knowledge and correlations,material selection and improvement,cell design and optimization,system control,power management,and monitoring of operation health for PEM fuel cells,along with main physics in PEM fuel cells for physics-informed machine learning.The objective of this review is three fold:(1)to present the most recent status of PEM fuel cell applications in the portable,stationary,and transportation sectors;(2)to describe the important fundamentals for the further advancement of fuel cell technology in terms of design and control optimization,cost reduction,and durability improvement;and(3)to explain machine learning,physics-informed deep learning,and AI methods and describe their significant potentials in PEM fuel cell research and development(R&D).

Hydrothermal base catalyzed depolymerization and conversion of technical lignin-An introductory review

Lignin represents the most significant potential source of sustainable aromatic compounds.Currently,the vast majority of technical lignin could be sourced from industrial paper production and in particular the Kraft process,where it is conventionally combusted for chemicals recovery and heat generation(e.g.for plant operation).While in recent years several efforts have concerned the conversion of native lignin(i.e.as found in nature)during biomass processing,there has also been significant focus on the“Base Catalyzed”conversion of technical lignin.This process is of significant interest,since it could be potentially integrated into existing Kraft mill infrastructure.The following review paper focuses on the development of the hydrothermal base catalyzed depolymerization(HBCD)of lignin,as a basis to produce valuable chemical compounds.Focus will be placed on NaOH catalyzed reactions in the aqueous phase,as this approach is considered the most promising.Focus is placed on reaction conditions and characterization of monomeric aromatic compounds from the HBCD approach.Oligomers,as largest product fraction,is also considered,however,these are seldom analyzed in detail in the literature and ideas on further use are scarce.The review also addresses findings in literature concerning the assessment of the solid,liquid,and gas product streams arising from HBCD.From this paper,process conditions for HBCD reactions can be derived and it is shown that the solid phase has a high potential for further valorization and downstream processing.

Lessons learned from the underrepresentation of women in STEM: AI-enabled solutions and more

The participation of women science,technology,engineering and mathematics(STEM)and energy fields is essential in advancing knowl-edge,securing economic growth,promoting prosperity and contribut-ing to the well-being of societies.Although the number of women in-volved in STEM fields has recently witnessed an increase in compar-ison to their natural counterparts,the“leaky pipeline”metaphor still applies.A greater number of women“leak out”and leave the educa-tional and professional pipelines at every stage of their lives,transition-ing from school to university to their careers,than men[1].The epitome of gender differences in the fields of STEM and energy industry can be captured by the disparities in representation of women in publications,salaries,senior rankings,annual productivity and resources allocation[2].