量产效率>22.3%的高阻密栅PERC太阳电池及性能研究

采用低压三步法通磷源扩散制备低掺杂浓度的p-n结,并应用于高阻密栅p型单晶硅钝化发射极局域背接触(PERC)太阳电池。通过增加第二步小氮的流量以改变扩散后硅片的方阻。随着方阻的增大,发射极表面掺杂浓度降低、俄歇复合降低、平均少子寿命增加。通过ECV测试,研究不同方块电阻对发射极掺杂浓度及结深的影响,结合发射极光电损耗机理的理论分析,确定优化的扩散后方块电阻180Ω/□及激光选择性掺杂区域方阻为80Ω/□,并对应细栅的数目为114。研究表明,随着发射极方块电阻的提高,太阳电池的短波响应显著提高,短路电流稳定提升80 mA,而通过对细栅线设计的优化,可抑制方阻提高对串联电阻及填充因子的影响,高方阻密栅PERC太阳电池的光电性能显著提升,电池效率稳定提升0.28%,转化效率达到22.3%,体现出高方阻密栅技术应用于PERC太阳电池的巨大潜力。     

电子束法沉积ITO薄膜及其光电性质的研究

用电子束蒸发制得了透明导电的ITO(indiumtin oxide)薄膜(厚3000—5000(?)),其方块电阻为4.5—20Ω/□,波长7000(?)时的透光率为80—95％。用x-线衍射分析方法测定了膜的组成与结构,用扫描电镜(SEM)观察了薄膜的形貌。薄膜的颗粒度为1—3μm,载流子浓度(N)为3.9×10~(19)cm~(-3),霍耳迁移率(μ_H)为94cm~2·V~(-1)·s~(-1),电阻率(ρ)为4.0×0~(-4)—2×10~(-3)Ω·cm,E_g为3.4eV。测得的Hall电压是负值,说明它是一种n型半导体。     

应用于太阳电池的单晶硅上化学镀镍工艺

研究了在P型单晶硅上扩散的N区发射极上选择性化学镀镍工艺,获得了较为优化的化学镀工艺过程,得到了均匀致密的镀层。其中针对单晶硅表面的特点,采取了浓酸浸泡和HF处理以及氯化钯的活化方法,使得镀层质量得以提高。进行了合金化处理温度对合金层的电阻率影响的研究,结果发现在N_2气氛下330℃的热处理将会促进具有最低方块电阻的Ni-Si合金的形成。在方块电阻为45Ω/□的发射极上,化学镀后得到了方块电阻为2Ω/□的Ni-Si合金层。     

衬底温度对AZO/Cu/AZO多层薄膜结构及光电特性的影响

采用射频磁控溅射和离子束溅射联合设备在玻璃衬底上制备出了具有良好附着性、低电阻率和高透过率的AZO/Cu/AZO多层薄膜.研究了衬底温度对薄膜的结构和光电特性影响.X射线衍射谱表明AZO/Cu/AZO多层薄膜是多晶膜,AZO层具有六角纤锌矿结构,最佳取向为(002)方向,Cu层具有立方结构.当三层薄膜制备过程中,衬底始终加热,衬底温度为100%℃时,制备的薄膜具有最高的品质因子2.26×10-2Ω-1,其方块电阻为11Ω·□-1,在波长500-800nm范围内平均透过率达到了87%.当制备靠近衬底的AZO层,衬底才加热时,发现衬底温度为250℃时,制备的多层薄膜光电特性最优,其方块电阻为8Ω·□-1,平均透过率为86%.     

a-Si:H(p)/c-Si(n)异质结太阳电池的模拟优化

通过AFORS-HET软件模拟了TCO/a-Si:H(p)/a-Si:H(i)/c-Si(n)/a-Si:H(i)/a-Si:H(n)/Ag结构的硅异质结电池中硅衬底电阻率、本征非晶硅薄膜厚度、发射极材料特性以及TCO功函数对电池性能的影响。结果表明:在其它参数不变的条件下,硅衬底电阻率越低,转换效率越高;发射极非晶硅薄膜厚度对短路电流有较大影响,发射极掺杂浓度低于7.0×10¹⁹cm^-3时,电池各项性能参数都极差;TCO薄膜功函数应大于5.2 eV,以保证载流子的输运收集。     

基于激光掺杂的SE+PERC单晶硅太阳电池关键工艺的研究

在现阶段主流太阳电池生产设备的水平条件下,研究了激光频率、初始方块电阻和烧结峰值温度对基于激光掺杂的选择性发射极(SE)+PERC单晶硅太阳电池电性能的影响。分别采用奥林巴斯显微镜和Halm电学性能测试仪,分析了不同频率的激光在硅片表面形成的光斑形貌,以及不同实验条件时电池的电性能变化趋势。结果表明,激光频率为220 kHz时有利于在硅片表面形成连续性且不重叠的光斑,形成最佳重掺杂区,从而提升电池转换效率;基于现有的常压扩散设备的掺杂水平,在确保硅片表面方块电阻均匀性的情况下,初始方块电阻选择120Ω/□更有利于提升电池的转换效率;烧结峰值温度为790℃时,更有利于在电池电极位置形成良好的欧姆接触,从而获得最佳的电池转换效率。     

Ga_(1-x)Al_xAs-GaAs太阳电池低阻接触研究

本文报道了pGa_(1-x)-Al_xAs-GaAs太阴电池的欧姆接触特性。用四探针法测定了Cr-Au、Ag-Zn、TiPdAu在pGaAs与pGa_(1-x)Al_xAs上的比接触电阻。在pGaAs上测出的比接触电阻分别为6.4×10~(-5)、9.4×10~(-5)和6.75×10~(-5)Ω-cm~2;在pGa_(1-x)Al_xAs上测出的比接触电阻分别为5.82×10~(14)、1.03×10~(-3)、5.02×10~(-4)Ω-cm~2(x≥0.8)。发现加热合金化和脉冲激光合金化方法效果相当。用离子刻蚀法刻蚀pGa_(1-x)Al_xAs,使电极直接与pGaAs接触时,比接触电阻值可降低一个数量级。效率高于15％(AM1)的太阳电池的串联电阻在1.0Ω以下。     

激光全掺杂制备太阳电池发射极的研究

采用波长532 nm的激光脉冲在n型单晶硅衬底上扫描预置的硼源,进行太阳电池发射极制备的研究。通过全激光掺杂获得方块电阻最低为30Ω/□的发射极,经过退火后少子寿命大幅度提升;在此基础上,初步制备的太阳电池的开路电压Uoc达到597 mV,转换效率为13.58%。研究表明,激光全掺杂是制备太阳电池发射极的有效方法。     

n型太阳电池硼扩散制备正面发射极工艺研究

对于n-PERT电池,硼扩散是形成p-n结的关键工艺并且直接影响电池性能。为优化正面硼扩散掺杂层的性能,研究液态源(BBr3)扩散过程中推进温度和推进时间对硼表面掺杂浓度和结深的影响,并且结合PC1D的模拟结果,分析不同的正面硼发射极对n-PERT太阳电池性能的影响。研究结果表明,推进温度在950～970℃范围变化时,随着推进温度的升高,结深由0.4μm增加到0.63μm,硼表面掺杂浓度由4.3×10¹⁹cm^-3增加到5.9×10¹⁹cm^-3;推进时间由25 min增加到40 min过程中,结深由0.47μm增加到0.64μm,硼表面掺杂浓度有较小的下降;当发射极表面浓度较低,结深较深时,有利于提升电池性能;该实验在模拟计算和工艺优化的基础上制备出效率为20.03%的nPERT电池。     

玻璃衬底和硅衬底沉积TZO透明导电薄膜的对比研究

利用直流磁控溅射法在室温水冷玻璃衬底和硅片衬底上制备出掺钛氧化锌(ZnO∶Ti)透明导电薄膜。SEM和XRD研究结果表明,两种衬底上的ZnO∶Ti薄膜均为为六角纤锌矿结构的多晶薄膜,且具有c轴择优取向。讨论了衬底对掺钛氧化锌透明导电薄膜光学、电学性能的影响。当玻璃衬底薄膜厚度为568nm时,薄膜电阻率达到最小值1.64×10-4Ω.cm,硅衬底上薄膜厚度为641nm时有最小电阻率2.69×10-4Ω.cm。两种衬底所制备薄膜都具有良好的附着性能,玻璃衬底薄膜样品在波长为500~800nm的可见光中平均透过率都超过了91%,硅衬底上薄膜样品的折射率约为2.05,ZnO∶Ti薄膜可以用作薄膜太阳电池的透明电极。     

Impact of sheet resistance on 2-D modeling of thin-film solar cells

A rigorous mathematical approach was used to find a relation between the transparent-conductive-oxide (TCO) sheet resistance ρ_S (Ω/□) of a thin-film solar cell and the parameter R (Ω) that describes the TCO resistance in a two-dimensional circuit model. Additionally, the mathematical relationship that connects experimentally derived series resistance R_S (Ω cm²) of the solar cell to the TCO sheet resistance ρ_S (Ω/□) and the bulk semiconductor resistivity ρ (Ω cm) was derived. It was found that the fill factor of the solar cell is governed by a reduced dimensionless TCO sheet resistance that depends only weakly on the type and quality of the solar cell. Parameters corresponding to thin-film Cu(In,Ga)Se₂, two-junction a-Si, and an ideal solar cell were used as concrete examples.     

薄膜厚度对ZnO:Ti透明导电薄膜光电性能的影响

利用直流磁控溅射法在室温水冷玻璃衬底上制备出可见光透过率高、电阻率低的掺钛氧化锌(ZnO∶Ti)透明导电薄膜。SEM和XRD研究结果表明,ZnO∶Ti薄膜为六角纤锌矿结构的多晶薄膜,且具有c轴择优取向。讨论了薄膜厚度对掺钛氧化锌透明导电薄膜光学、电学性能的影响。当薄膜厚度为835nm时,薄膜具有最低电阻率3.34×10-4Ω.cm。所制备薄膜附着性能良好,在波长为500～800nm的可见光中平均透过率均超过91%,ZnO∶Ti薄膜可用作薄膜太阳电池和液晶显示器的透明电极。     

发射极掺杂工艺对产业化IBC太阳电池性能的影响

主要对n型IBC太阳电池结构的发射极硼掺杂工艺进行优化设计,并通过ENDA2模拟软件对实验结果进行验证分析,通过复合损失分析,研究不同发射极硼扩工艺对产业化IBC太阳电池电性能的影响.实验结果表明,采用较高推进温度的硼扩散工艺,获得发射极方阻98Ω/sq,该发射极具有最低的表面浓度1.68×1019 cm-3和最深结深...     

Sheet resistance uniformity in drive-in step for different multi-crystalline silicon wafer dispositions

In this work, we present a study of emitters realized using different configurations of the silicon wafers in the quartz boat. The phosphorous liquid source is sprayed onto p-type multi-crystalline silicon substrates and the drive-in is made at high temperature in a muffle furnace. Three different configurations of the wafers in the boat are tested: separated, back to back and compact block of wafers. A fourth configuration is also used in source-receptor mode. The emitter phosphorous concentration profile is obtained by SIMS analysis. The resulting emitters are characterized by sheet resistance measurements and a comparison is made between the wafers within the same batch and from one batch to another. The uniformity and the standard deviation of the sheet resistance are calculated in each case. The emitter sheet resistance mapping of the wafer set in the middle of the boat for a given process gives a mean R_sq 14.66 Ω/sq with a standard deviation of 1.76% and uniformity of 18.7%. Standard deviations of 2.116% and 1.559% are obtained for wafers in the batch when using the spaced and compact configurations, respectively. The standard deviation is reduced to 0.68% when the wafers are used in source/receptor mode. A comparison is also made between wafers with different dilution of phosphorous source in ethanol.From these results we can conclude that the compact configuration offers better uniformity and lower standard deviation. Furthermore, when combined with the source-receptor configuration these parameters are significantly improved.This study allows the experimenter to identify the technological parameters of the solar cell emitter manufacturing and target precisely the desired values of the sheet resistance while limiting the number of rejected wafers.     

Highly stable transparent and conducting gallium-doped zinc oxide thin films for photovoltaic applications

Transparent and highly conducting gallium zinc oxide (GZO) films were successfully deposited by RF sputtering at room temperature. A lowest resistivity of ∼2.8×10⁻⁴ Ω cm was achieved for a film thickness of 1100 nm (sheet resistance ∼2.5 Ω/□), with a Hall mobility of 18 cm²/V s and a carrier concentration of 1.3×10²¹ cm⁻³. The films are polycrystalline with a hexagonal structure having a strong crystallographic c-axis orientation. A linear dependence between the mobility and the crystallite size was obtained. The films are highly transparent (between 80% and 90% including the glass substrate) in the visible spectra with a refractive index of about 2, very similar to the value reported for the bulk material. These films were applied to single glass/TCO/pin hydrogenated amorphous silicon solar cells as front layer contact, leading to solar cells with efficiencies of about 9.52%. With the optimized deposition conditions, GZO films were also deposited on polymer (PEN) substrates and the obtained results are discussed.     

Characteristics of flexible indium tin oxide electrode grown by continuous roll-to-roll sputtering process for flexible organic solar cells

The preparation and characteristics of flexible indium tin oxide (ITO) electrodes grown on polyethylene terephthalate (PET) substrates using a specially designed roll-to-roll sputtering system for use in flexible organic solar cells are described. It was found that both electrical and optical properties of the flexible ITO electrode were critically dependent on the Ar/O₂ flow ratio in the continuous roll-to-roll sputter process. In spite of the low substrate temperature (<50 °C), we can obtain the flexible ITO electrode with a sheet resistance of 47.4 Ω/square and an average optical transmittance of 83.46% in the green region of 500-550 nm wavelength. Both X-ray diffraction and field emission scanning electron microscopy analysis results showed that all flexible ITO electrodes grown on the PET substrate were amorphous with a very smooth and featureless surface, regardless of the Ar/O₂ flow ratio due to the low substrate temperature, which is maintained by a cooling drum. In addition, the flexible ITO electrode grown on the Ar ion-beam-treated PET substrates showed more stable mechanical properties than the flexible ITO electrode grown on the wet-cleaned PET substrates, due to an increased adhesion between the flexible ITO and the PET substrates. Furthermore, the flexible organic solar cell fabricated on the roll-to-roll sputter-grown flexible ITO electrode at an optimized condition exhibited a power conversion efficiency of 1.88%. This indicates that the roll-to-roll sputtering technique is a promising continuous sputtering process in preparing flexible transparent electrodes for flexible solar cells or displays.     

Optimized resistivity of p-type Si substrate for HIT solar cell with Al back surface field by computer simulation

For HIT (heterojunction with intrinsic thin-layer) solar cell with Al back surface field on p-type Si substrate, the impacts of substrate resistivity on the solar cell performance were investigated by utilizing AFORS-HET software as a numerical computer simulation tool. The results show that the optimized substrate resistivity (R_op) to obtain the maximal solar cell efficiency is relative to the bulk defect density, such as oxygen defect density (D_od), in the substrate and the interface defect density (D_it) on the interface of amorphous/crystalline Si heterojunction. The larger D_od or D_it is, the higher R_op is. The effect of D_it is more obvious. R_op is about 0.5 Ω cm for D_it = 1.0 × 10¹¹/cm², but is higher than 1.0 Ω cm for D_it = 1.0 × 10¹²/cm². In order to obtain very excellent solar cell performance, Si substrate, with the resistivity of 0.5 Ω cm, D_od lower than 1.0 × 10¹⁰/cm³, and D_it lower than 1.0 × 10¹¹/cm², is preferred, which is different to the traditional opinion that 1.0 Ω cm resistivity is the best.     

The superiority of Ti plate as the substrate of dye-sensitized solar cells

The photovoltaic properties of dye-sensitized solar cells (DSCs) based on several types of substrates, FTO, Ti and stainless steel, were investigated. The sheet resistances of the substrates were correlated to the photovoltaic properties. The efficiency of the DSC using Ti substrate was higher than that of the DSCs using stainless steel and FTO. For the large-size DSCs based on FTO, the metal track is an important component to retain the decrease in cell performance due to the relatively high sheet resistance of FTO. To minimize the internal resistance of DSCs, the Ti sheet was used as a support of nano-crystalline TiO₂ due to the low sheet resistance. Although the IPCE of DSCs based on Ti substrate was lower than that of DSCs based on FTO in the range from 400 to 500 nm, the DSC based on Ti substrate showed the higher IPCE in red region due to the light reflecting on Ti substrate. The efficiency of 3.2% for the DSC based on Ti substrate was obtained with a Jsc , Voc 0.75 V, and FF 0.610. This result shows that the Ti plate has superiority for producing the large DSCs without metal track and reduces the cost of DSCs.