Back interface passivation for ultrathin Cu(In,Ga)Se_(2) solar cells with Schottky back contact: A trade-off of electrical effects

Back interface passivation reduces the back recombination of photogenerated electrons, whereas aggravates the blocking of hole transport towards back contact, which complicate the back interface engineering for ultrathin CIGSe solar cells with a Schottky back contact. In this work, theoretical explorations were conducted to study how the two contradictory electrical effects impact cell performance. For ultrathin CIGSe solar cells with a pronounced Schottky potential barrier(E_(h)> 0.2 eV), back interface passivation produces diverse performance evolution trends, which are highly dependent on cell structures and properties. Since a back Ga grading can screen the effect of reduced recombination of photogenerated electrons from back interface passivation, the hole blocking effect predominates and back interface passivation is not desirable. However, when the back Schottky diode merges with the main pn junction due to a reduced absorber thickness,the back potential barrier and the hole blocking effect is much reduced on this occasion. Consequently, cells exhibit the same efficiency evolution trend as ones with an Ohmic contact, where back interface passivation is always advantageous.The discoveries imply the complexity of back interface passivation and provide guidance to manipulate back interface for ultrathin CIGSe solar on TCOs with a pronounced Schottky back contact.

Back contact interfacial modification mechanism in highly-efficient antimony selenide thin-film solar cells

Antimony selenide(Sb_(2)Se_(3))is a potential photovoltaic(PV)material for next-generation solar cells and has achieved great development in the last several years.The properties of Sb_(2)Se_(3)absorber and back contact influence the PV performances of Sb_(2)Se_(3)solar cells.Hence,optimization of back contact characteristics and absorber orientation are crucial steps in raising the power conversion efficiency(PCE)of Sb_(2)Se_(3)solar cells.In this work,MoO2was introduced as an intermediate layer(IL)in Sb_(2)Se_(3)solar cells,and comparative investigations were conducted.The growth of(211)-oriented Sb_(2)Se_(3)with large grains was facilitated by introducing the MoO2IL with suitable thickness.The MoO2IL substantially lowered the back contact barrier and prevented the formation of voids at the back contact,which reduced the thickness of the MoSe2interface layer,inhibited carrier recombination,and minimized bulk and interfacial defects in devices.Subsequently,significant optimization enhanced the open-circuit voltage(VOC)of solar cells from 0.481 V to 0.487 V,short-circuit current density(JSC)from 23.81 m A/cm^(2)to 29.29 m A/cm^(2),and fill factor from 50.28%to 57.10%,which boosted the PCE from 5.75%to 8.14%.

Deep level transient spectroscopy investigation of deep levels in CdS/CdTe thin film solar cells with Te:Cu back contact

Deep levels in Cds/CdTe thin film solar cells have a potent influence on the electrical property of these devices. As an essential layer in the solar cell device structure, back contact is believed to induce some deep defects in the CdTe thin film. With the help of deep level transient spectroscopy （DLTS）, we study the deep levels in CdS/CdTe thin film solar cells with Te：Cu back contact. One hole trap and one electron trap are observed. The hole trap H1, localized at Ev＋0.128~eV, originates from the vacancy of Cd （VCd. The electron trap E1, found at Ec-0.178~eV, is considered to be correlated with the interstitial Cui= in CdTe.

Analysis of the interdigitated back contact solar cells:The n-type substrate lifetime and wafer thickness

The n-type silicon integrated-back contact（IBC） solar cell has attracted much attention due to its high efficiency,whereas its performance is very sensitive to the wafer of low quality or the contamination during high temperature fabrication processing, which leads to low bulk lifetime τbulk. In order to clarify the influence of bulk lifetime on cell characteristics, two-dimensional（2D） TCAD simulation, combined with our experimental data, is used to simulate the cell performances, with the wafer thickness scaled down under various τbulk conditions. The modeling results show that for the IBC solar cell with high τbulk,（such as 1 ms-2 ms）, its open-circuit voltage V oc almost remains unchanged, and the short-circuit current density J sc monotonically decreases as the wafer thickness scales down. In comparison, for the solar cell with low τbulk（for instance, 〈 500 μs） wafer or the wafer contaminated during device processing, the V oc increases monotonically but the J sc first increases to a maximum value and then drops off as the wafer＇s thickness decreases. A model combing the light absorption and the minority carrier diffusion is used to explain this phenomenon. The research results show that for the wafer with thinner thickness and high bulk lifetime, the good light trapping technology must be developed to offset the decrease in J sc.

Study of Back Contacts for CdTe Solar Cells

ZnTe/ZnTe∶Cu layer is used as a complex back contact. The parameters of CdTe solar cells with and without the complex back contacts are compared. The effects of un-doped layer thickness, doped concentration and post-deposition annealing temperature of the complex layer on solar cells performance are investigated.The results show that ZnTe/ZnTe∶Cu layer can improve back contacts and largely increase the conversion efficiency of CdTe solar cells. Un-doped layer and post-deposition annealing of high temperature can increase open voltage. Using the complex back contact, a small CdTe cell with fill factor of 73.14% and conversion efficiency of 12.93% is obtained.

Influence of using amorphous silicon stack as front heterojunction structure on performance of interdigitated back contact-heterojunction solar cell （IBC-HJ）

Interdigitated back contact-heterojunction （IBC-HJ） solar cells can have a conversion efficiency of over 25%. However, the front surface passivation and structure have a great influence on the properties of the IBC-HJ solar cell. In this paper, detailed numerical simulations have been performed to investigate the potential of front surface field （FSF） offered by stack of n-type doped and intrinsic amorphous silicon （a-Si） layers on the front surface of IBC-HJ solar cells. Simulations results clearly indicate that the electric field of FSF should be strong enough to repel minority carries and cumulate major carriers near the front surface. However, the overstrong electric field tends to drive electrons into a-Si layer, leading to severe recombination loss. The n-type doped amorphous silicon （n-a-Si） layer has been optimized in terms of doping level and thickness. The optimized intrinsic amorphous silicon （i-a-Si） layer should be as thin as possible with an energy band gap （Es） larger than 1.4 eV. In addition, the simulations concerning interface defects strongly suggest that FSF is essential when the front surface is not passivated perfectly. Without FSF, the IBC-HJ solar cells may become more sensitive to interface defect density.

Influence of Cu_xS back contact on CdTe thin film solar cells

We present a detailed study on CuxS polycrystalline thin films prepared by chemical bath method and utilized as back contact material for CdTe solar cells.The characteristics of the films deposited on Si-substrate are studied by XRD.The results show that as-deposited CuxS thin film is in an amorphous phase while after annealing,samples are in polycrystalline phases with increasing temperature.The thickness of CuxS thin films has great impact on the performance of CdS/CdTe solar cells.When the thickness of the film is about 75 nm the performance of CdS/CdTe thin film solar cells is found to be the best.The energy conversion efficiency can be higher than 12.19%,the filling factor is higher than 68.82% and the open-circuit voltage is more than 820 mV.

海上窄压力窗口控压固井浆柱结构设计方法

针对海上油气井窄压力窗口固井顶替效率低下的技术难题,通过轻钻井液的施加以优化浆柱结构以及施加环空回压的方法实现安全高效固井的目标。考虑停泵压胶塞环空回压值≯5 MPa、冲洗液环空紊流接触时间>10min以及注替结束井筒自压稳3个关键技术要求,合理优化固井浆柱结构,计算控压固井全过程井筒当量循环密度(ECD),使井筒ECD在安全密度窗口内,形成了海上窄压力窗口控压固井浆柱结构设计方法。以乐东10-1气田某高温高压井为例,优化设计了该井的浆柱结构,并模拟计算了控压固井全过程井筒ECD及紊流接触时间。结果表明:轻钻井液用量为14~50 m^(3)且密度在1.822~2.142 g/cm^(3)之间、冲洗液用量>13 m^(3)且密度在2.36~2.45 g/cm^(3)之间、水泥浆密度在2.4~2.51 g/cm^(3)之间,可实现冲洗液紊流接触时间>10 min且满足压稳不漏的固井要求。该设计方法可实现海上窄压力窗口井安全施工和提高固井顶替效率的要求。

背接触电池的低温主栅工艺分析

阐述主栅材料、电极结构和烘干工艺方面对背接触电池的影响,通过优化相关参数实现背接触电池的高转换效率,从而获得成本较低、生产节奏较快、效率更优的主栅工艺,促进生产发展。

背接触电池的细栅线工艺分析

阐述不同细栅线间距和细栅线横截面积在背接触电池上对效率的影响。通过实验验证,确定细栅线间距需要进行不断缩小、密化,细栅线的横截面积需要不断增加、宽化,获得优异的电池效率。

Understanding the Properties of Silicon Solar Cells Aluminium Contact Layers and Its Effect on Mechanical Stability

As the thickness of silicon solar wafer and solar cells becomes thinner, the cells are subjected to high stress due to the thermal coefficient mismatch induced by metallization process. Handling and bowing problems associated with thinner wafers become increasingly important, as these can lead to cells cracking and thus to high yield losses. The goal of this work to provide experimental understanding of Al rear side microstructure development and mechanical properties as well as correlate the obtained results with fracture behaviour of the cell. It is shown that the aluminium back contact has a complex microstructure, consisting of five main components: 1) the back surface field layer;2) a eutectic layer;3) spherical (3 - 5 μm) hypereutectic Al-Si particles surrounded by a thin aluminium oxide layer (200 nm);4) a bis- muth-silicate glass matrix;and 5) pores (14 vol%). It was concluded that the eutectic layer thickness and waviness depends on Al particle size, amount of Al paste and textured surface roughness of silicon wafers. The Young’s modulus of the Al-Si particles is estimated by nano-indentation and the overall Young’s modulus is estimated on the basis of bowing measurements and found to be ~43 GPa. It was found, that there is a relation between aluminium paste composition, eutectic layer thickness, mechanical strength and bowing of solar cells. Three main parameters were found to affect the mechanical strength of mc-silicon solar cells with an aluminium contact layer, namely the eutectic layer thickness and uniformity, the Al layer thickness (which results from the Al particle size and its distribution), and the amount of porosity and the bismuth glass fraction.

NUMERICAL STUDY ON FLANGING AND SPRINGBACK OF STAMPED THICK METAL PLATE

A quasi-three-dimensional shell element model, which can beeffectively used to simulate the flanging and spring-backdeformation, is introduced into the independently developed CAEsoftware, KMAS, In this model, a double surface contact algorithm,which allows the gap between punch and die to change, and a spring-back treatment scheme based on finite element meshing are described.And then the flanging and spring-back deformations of the retractor'skickstand of a railcar made of stamped thick metal plate arenumerically simulated. The simulation results of flanging deformationare compared with those of international commercial software,PAM-STAMP, and experimental ones. Finally, a predicting scheme ofspring-back quantily for this problem is given.

Effects of back gate bias on radio-frequency performance in partially depleted silicon-on-inslator nMOSFETs

The effects of back gate bias(BGEs) on radio-frequency(RF) performances in PD SOI n MOSFETs are presented in this paper. Floating body(FB) device, T-gate body-contact(TB) device, and tunnel diode body-contact(TDBC) device, of which the supply voltages are all 1.2 V, are compared under different back gate biases by different figures of merit, such as cut-off frequency( fT), maximum frequency of oscillation( fmax), etc. Because of the lack of a back gate conducting channel, the drain conductance(gd) of TDBC transistor shows a smaller degradation than those of the others, and the trans-conductance(gm) of TDBC is almost independent of back gate bias. The values of fT of TDBC are also kept nearly constant under different back gate biases. However, RF performances of FB and TB each show a significant degradation when the back gate bias is larger than ～ 20 V. The results indicate that TDBC structures could effectively improve the back gate bias in RF performance.

Backlund变换理论发展简述及其新方法

本文首先简要介绍Bcklund变换理论的发展过程,然后介绍一种寻找微分方程Bcklund变换的新方法——wahlquist-Estabrook过程。该方法是目前处理微分方程Bcklund问题的最有效方法.尽管该方法在理论上可应用于任意维数的偏微分方程组,但是实际上它所能处理的主要是二维问题。例如,在应用该方法处理完整Navicr-Stokcs方程(四维问题)时,所得到的是无意义结果.但是,在应用该方法处理定常二维Navicr-Stokcs方程时,确实可以得到正常的Bcklund映射,以及Bcklund变换.

新型硒化锑薄膜太阳电池背接触优化

硒化锑(Sb_(2)Se_(3))具有低毒、原材料丰富和光电性能优异等优点,被认为是最具有发展潜力的薄膜太阳电池光吸收层材料之一.但目前Sb_(2)Se_(3)薄膜太阳电池光电转换效率与碲化镉、铜铟镓硒和钙钛矿等太阳电池相比仍存在较大差距.限制Sb_(2)Se_(3)薄膜太阳电池光电转换效率进一步提升的关键因素之一是,太阳电池结构中Mo背电极和Sb_(2)Se_(3)薄膜构建的背接触界面处容易形成较高的势垒,降低载流子的抽取效率.本工作则对Mo背电极进行热处理生成缓冲层MoO_(2)薄膜,发现缓冲层MoO_(2)的引入,可有效地促进Sb_(2)Se_(3)薄膜的择优取向生长,同时实现太阳电池Mo/MoO_(2)/Sb_(2)Se_(3)背接触势垒降低,相应的填充因子、开路电压和短路电流密度均获得显著提高,构建的太阳电池光电转换效率从5.04%提升至7.05%.

铜锑硫薄膜太阳电池的数值模拟研究

用SCAPS构建了铜锑硫薄膜太阳电池模型,计算了器件的性能。分别研究了吸收层厚度、载流子浓度、缺陷密度和背电极功函数对器件性能的影响。结果表明,过薄的吸收层对绿光和红光吸收不充分,1.5~3μm厚的吸收层能满足光谱吸收要求。当受主浓度为2×10^(18)cm^(-3)时,器件光电转换效率最高。缺陷密度大于10^(-14)cm^(-3)时,器件的光电转换效率急剧降低。贫铜富硫气氛制备铜锑硫可以提高受主浓度,减小开路电压亏损,也可以抑制硫空位缺陷形成,从而提高器件的光电转换效率。功函数较高的材料能降低背电极势垒,减少载流子在背电极复合。材料参数优化后,器件的光电转换效率最高为21.74%。

基于氯化铯背接触处理优化硒化锑薄膜太阳电池性能

本文使用气相输运沉积的方式制备了硒化锑(Sb_(2)Se_(3))薄膜太阳电池,并采用氯化铯(CsCl)溶液对器件上界面进行处理,同时对薄膜和器件进行了一系列表征。研究发现,CsCl溶液的背接触处理不仅可以提高器件的载流子收集以及降低上界面复合,还可以优化薄膜的结晶性、表面粗糙度和光电性能。基于FTO/CdS/Sb_(2)Se_(3)/CsCl/Au的器件结构,得到了转换效率为6.32%的高效Sb_(2)Se_(3)薄膜太阳电池,比基础器件效率提升了12%。本文的工作对Sb_(2)Se_(3)薄膜太阳电池未来的研究有一定的指导作用,其他同类型半导体光伏器件也可借鉴。

四辊可逆粗轧支承辊的剥落分析与使用维护

结合某钢铁企业1780 mm热带连轧机粗轧支承辊使用跟踪情况,对支承辊的接触疲劳剥落机理进行深入分析,并提出四辊可逆粗轧支承辊的使用与维护方案。实践表明,通过增大磨削量和增加表面检测可有效避免支承辊剥落现象的发生。

n型隧穿氧化层钝化背接触太阳能电池发射极激光硼掺杂工艺

在n型隧穿氧化层钝化背接触(TBC)太阳能电池发射极制程中引入激光掺杂可快速实现发射极图案化制作,简化电池制作流程。通过激光将硼硅玻璃(BSG)中的硼掺入多晶硅层中,形成图案化的掺硼多晶硅层。研究了不同激光参数及掺杂次数对TBC太阳能电池发射极钝化性能和方块电阻的影响,实验结果表明,当激光功率为70 W、掺杂次数为2次时,太阳能电池发射极可获得良好的钝化效果和合适方阻,其中掺杂浓度达到8.1×10^(19)cm^(-3),隐开路电压>723 mV,方块电阻约为150Ω/□。制备的TBC太阳能电池的平均光电转换效率可达24.691%,短路电流密度为42.31 mA/cm^(2),开路电压为718.7 mV,填充因子为81.2%。

不同薄膜对n型IBC太阳电池性能的影响

叉指背接触式(IBC)太阳电池因正面没有金属栅线遮挡,具有较高的光电转换效率。但由于IBC太阳电池在制备过程中需要采用光刻掩模技术进行发射极和背电场隔离,导致工艺流程复杂、电池片稳定性较差,难以实现大规模生产。研究了不同厚度的SiO_(2)薄膜、SiNx薄膜和SiO_(2)-SiNx叠层薄膜对IBC太阳电池钝化性能、减反射效果、热稳定性能和电性能的影响,实验结果表明,SiO_(2)-SiNx叠层薄膜在较宽的光谱范围内减反射效果更佳,高温热生长的20 nm厚的SiO_(2)薄膜便表现出良好的热稳定性,当选用SiO_(2)-SiNx(厚度分别为20和40 nm)叠层薄膜时,制备的IBC太阳电池光电转换效率稳定,可达24.1%,对应的开路电压为698 mV,短路电流密度为43.25 mA/cm^(2),填充因子为79.87%。