Effect of hydrogen annealing on characteristics of polycrystalline silicon

The characteristics of mc-Si used for solar cells during H2 ambient annealing at 800-1200 ℃ were investigated by means of FTIR and QSSPCD. The results reveal that grain boundaries or defects in mc-Si may facilitate the formation of oxygen precipitates, and the formation of oxygen precipitates has deleterious effect on the lifetime of mc-Si. Decreasing lifetime could result from the formation of new recombination during annealing. Additionally, It is found that hydrogen may facilitate the formation of oxygen precipitates in mc-Si. On the other hand, the diffusion of hydrogen may passivate the defects/boundaries and it is beneficial to the lifetime of mc-Si.     

晶硅衬底参数对太阳电池输出特性的影响

利用晶硅电池模拟软件PC1D研究晶硅衬底的厚度、少子寿命及掺杂浓度对电池输出特性的影响规律。结果表明:晶硅衬底的厚度对电池输出特性的影响与其少子的扩散长度有关,衬底厚度的减小有利于其开路电压的提高,存在一最佳厚度值使其转换效率、短路电流及填充因子最高;当少子的扩散长度远大于衬底厚度时,电池的输出特性几乎与衬底厚度无关;当衬底少子扩散长度与衬底厚度的比值为2.5~3.0时,电池的转换效率最高;晶硅衬底的掺杂浓度在5×1015~1×1017cm 3之间,即电阻率在0.2~3.0.cm范围内时,晶硅电池能获得良好的输出特性。     

a-Si/c-Si heterojunction solar cells on SiSiC ceramic substrates

Silicon thin-film solar cells are considered to be one of the most promising cells in the future for their potential advantages, such as low cost, high efficiency, great stability, simple processing, and none-pollution. In this paper, latest progress on poly-crystalline silicon solar cells on ceramic substrates achieved by our group was reported. Rapid thermal chemical vapor deposition (RTCVD) was used to deposited poly-crystalline silicon thin films, and the grains of as-grown film were enlarged by Zone-melting Recrystallization (ZMR). As a great changein cell's structure, traditional diffused pn homojunction was replaced by a-Si/c-Si heterojunction, which lead is to distinct improvement in cell's efficiency.A conversion efficiency of 3.42% has been achieved on 1cm2 a-Si/c-Si heterojunction solar cell ( Isc =16.93 mA, Voc =310.9 mV, FF =06493, AM =1.5 G,24 ℃), while the cell with diffused homojunction only gotan efficiency of 0.6%. It indicates that a-Si emitter formed at low temperature might be more suitable for thin film cell on ceramics.     

Effect of Grain Boundaries on the Performance of Thin-Film-Based Polycrystalline Silicon Solar Cells: A Numerical Modeling

Solar cells/photovoltaic, a renewable energy source, is appraised to be the most effective alternative to the conventional electrical energy generator. A cost-effective alternative of crystalline wafer-based solar cell is thin-film polycrystalline-based solar cell. This paper reports the numerical analysis of dependency of the solar cell parameters (i.e., efficiency, fill factor, open-circuit voltage and short-circuit current density) on grain size for thin-film-based polycrystalline silicon (Si) solar cells. A minority carrier lifetime model is proposed to do a correlation between the grains, grain boundaries and lifetime for thin-film-based polycrystalline Si solar cells in MATLAB environment. As observed, the increment in the grain size diameter results in increase in minority carrier lifetime in polycrystalline Si thin film. A non-equivalent series resistance double-diode model is used to find the dark as well as light (AM1.5) current–voltage (I-V) characteristics for thin-film-based polycrystalline Si solar cells. To optimize the effectiveness of the proposed model, a successive approximation method is used and the corresponding fitting parameters are obtained. The model is validated with the experimentally obtained results reported elsewhere. The experimentally reported solar cell parameters can be found using the proposed model described here.     

Improved photovoltaic performance of dye-sensitized solar cells by carbon-ion implantation of tri-layer titania film electrodes

TiO2tri-layer structure films were modified by C-ions implantation for improving the photovoltaic performance of dye-sensitized solar cells(DSSCs), in which the structure of TiO2 changes from rutile to anatase and the sizes of TiO2 particles increase. The optimal concentration of ions implantation for C-implanted cells is 19 1015 atom cm-2,and the maximum conversion efficiency of 5.32 % is achieved(luminous intensity of 1 sun, light irradiance of AM1.5G),which is 25.2 % higher than that of unimplanted cell. The significant improvement in conversion efficiency by carbonion implantation is contributed to reducing charge recombination and enhancing the light-harvesting ability, as indicated from incident photon-to-collected electron conversion efficiency(IPCE) and ultraviolet-visible(UV-Vis) measurements. Furthermore, the charge carrier's lifetime in the trilayer titania films is prolonged after carbon-ion implantations.     

中间退火处理对AlMgSiCu铝合金冷轧板组织性能的影响

利用拉伸试验机、TEM透射电镜和XRD,研究了中间退火处理对6000系AlMgSiCu铝合金冷轧板力学性能和组织织构演变的影响。结果表明:经300 ℃×2 h和400 ℃×2 h的中间退火处理后,AlMgSiCu合金强度指标并未发生明显的改变。加工硬化指数(n)值和塑性应变比(r)值随中间退火温度的提高,呈现增加的趋势。经400 ℃×2 h中间退火处理后,n值达到了0.286,r值达到了0.623,大部分晶粒已演变为等轴晶粒。试样基体内主要存在3种形式的第二相,尺寸在1 μm左右的AlFeMnSi颗粒相,宽度在0.1 μm左右的长棒状AlMgSiCu相和球状Si颗粒相。长棒状AlMgSiCu相随着中间退火温度的升高先析出后溶解。无中间退火的板材,Brass{011}<211>织构和S{123}<634>织构的体积分数最高,分别达到了13.9%和25.7%。经400 ℃×2 h中间退火的试样,以Cube{001}<100>织构为主,体积分数达到了24.3%,r-Cube织构达到了10.5%。     

含锡取向硅钢高温二次再结晶退火过程中抑制剂的析出特点

采用透射电镜研究了含锡取向硅钢高温二次再结晶退火过程中抑制剂的析出行为,分析了抑制剂对初次再结晶的抑制作用。结果表明,析出物除了常规的AlN和MnS外,还有少量Sn单质;其中AlN和MnS相是主要抑制剂,具有强烈的抑制作用;少量Sn相起辅助抑制作用,控制析出物AlN的尺寸和数量,有助于主抑制剂的弥散分布。抑制剂在600~700 ℃时开始析出长大,900 ℃显著长大,1020 ℃平均尺寸达到最大值;抑制剂的尺寸随退火温度升高而增大,体积分数、分布密度则先增大后减少。当退火温度达到1000 ℃时,析出物平均粒径约50.3 nm,体积分数最大约3.81%,分布密度约5.9×10¹⁴ 个/cm³。根据试验和Zener因子综合判定抑制力,Zener因子随退火温度升高而增加,在900 ℃达到最大139,析出物分布密度达到最大8.9×10¹⁴个/cm³;在1020 ℃时,Zener因子几乎为零,完成二次再结晶过程。     

CSP工艺下稀土冷轧板退火过程中第二相析出的定量研究

研究了CSP工艺下稀土冷轧板冷轧后退火过程中的第二相析出行为,模拟了某企业685 ℃×9 h退火工艺,利用光学显微镜和X射线衍射仪分析了退火前后的微观组织和宏观织构的变化;采用非水电解分离法从试验钢中提取第二相粒子,并利用X射线衍射分析了第二相析出物类型;再使用化学法对退火过程中第二相析出量的变化进行了定量分析,并结合析出动力学计算分析第二相析出规律。结果表明,经过该退火工艺后,晶粒从典型的纤维状冷轧组织演变为再结晶饼形晶粒,非{111}织构有所减弱,{111}织构有所增强;试验钢中的第二相类型主要为MnS、Fe₃C和AlN,MnS在退火过程中几乎不析出,Fe₃C主要在室温到570 ℃升温过程中析出,AlN随着退火温度的升高而不断析出,在685 ℃附近析出最快。     

Efficient polymer solar cell modules

Polymer solar cell modules based on the standard polymer–fullerene system of to-date, P3HT–PCBM, have been prepared and characterized. We have observed a loss of only 20% when up-scaling the active area of the solar cell by a factor somewhat larger than 10. An average solar cell efficiency of 3% and a module efficiency of 1.9% for three serially interconnected solar cells of 5.4 cm² each are reported. The route for further optimization of module performance is discussed based on analyzing the existing loss factors within this design.     

Dye-sensitized solar cells based on Cr-doped TiO_2 nanotube photoanodes

The effect of chromium doping on the photovoltaic efficiency of dye-sensitized solar cells(DSSCs) with anodized TiO_2 nanotubes followed by an annealing process was investigated. Cr-doped TiO_2 nanotubes(CrTNs) with different amounts of chromium were obtained by anodizing of titanium foils in a single-step process using potassium chromate as the chromium source. Film features were investigated by scanning electron microscopy(SEM), X-ray diffraction(XRD), energy-dispersive X-ray spectroscopy(EDX), and ultraviolet-visible(UV-Vis) spectroscopy. It is clearly seen that highly ordered TiO_2 nanotubes are formed in an anodizing solution free of potassium chromate, and with a gradual increase in the potassium chromate concentration, these nanotube structures change to nanoporous and compact films without porosity. The photovoltaic efficiencies of fabricated DSSCs were characterized by a solar cell measurement system via the photocurrent-voltage(I-V) curves. It is found that the photovoltaic efficiency of DSSCs with CrTNsl sample is improved by more than three times compared to that of DSSCs with undoped TNs. The energy conversion efficiency increases from 1.05 % to 3.89 % by doping of chromium.     

钙钛矿太阳能电池稳定性的研究进展

回顾了钙钛矿太阳能电池的发展历程,总结了影响钙钛矿太阳能电池稳定性的几个重要因素,包括水汽、氧气、光照和高温条件对钙钛矿层的化学稳定性以及电子传输层(ETL)、空穴传输层(HTL)和制备工艺对电池稳定性的影响。对稳定机制进行了分析,提出了改善稳定性的一些方法,并根据目前的研究成果展望了钙钛矿太阳能电池的发展趋势。     

PREPARATION AND STRVCTURAL EVOLUTION OF TiO_2 THIN FILMS BY LOW PRESSURE MOCVD

1. IntroductionTitanium dioxide (TiO2) films are widely used for electrical and optical applications because of its high dielectric constant, its chemical stability and its high refractive i.de.[1--2].Tioz thin films can be prepared by various thin film deposition techniquesl3--8]. Amongthese techniques, chemical vapor deposition (CVD) is considered as a useful method to deposit high quality thin films with large area uniformity and well--controlled stoichiometry.Crystalline TiOZ exists th…     

Effects of annealing conditions on the properties of TiO2/ITO-based photoanode and the photovoltaic performance of dye-sensitized solar cells

Photovoltaic performance of dye-sensitized solar cell (DSSC) is enhanced by a two-step annealing process of the photoanode. The 1st-step of annealing is performed in oxygen at 450 °C for 30 min which effectively removes the residual organics originated from the TiO₂ precursor pastes. This enhances the dye adsorption on the TiO₂ nanoparticles and raises the short-circuit current density (J_SC). The 2nd-step of annealing is performed in nitrogen at 450 °C for 10 min which removes extra oxygen atoms resulted from the incorporation of oxygen atoms into the tin-doped indium oxide (ITO) film during the 1st-step of annealing. This reduces the sheet resistance of ITO and thereby enhances the fill factor (FF). With the enhanced J_SC of 15.9mAcm⁻² and FF of 0.65, the AM1.5 solar to electric conversion efficiency (η) of DSSC reaches 6.7% which is better than that based on the conventional one-step air annealing (η = 5.53%, J_SC = 14.08 mA cm⁻², FF = 0.6).     

连续退火工艺对4.5%Cr冷轧耐候钢组织性能的影响

利用Multipas退火试验机模拟连续退火工艺,研究了退火工艺对4.5%Cr冷轧耐候钢组织性能的影响。结果表明,随着退火温度的升高,试验钢的强度先降低后增加,当退火温度为830 ℃时,强度最高,屈服强度均值为353 MPa,抗拉强度均值约为621 MPa。冷速(50 ℃/s、30 ℃/s)对试验钢强度影响有限。当退火温度≤800 ℃时,试验钢的组织只发生了回复再结晶,组织由铁素体、珠光体和碳化物组成。当退火温度＞800 ℃,铁素体组织发生了奥氏体化,冷却后形成了贝氏体。当Cr含量(质量分数)提高至4.5%,试验钢的相对腐蚀速率为26%(相对于Q345B钢),相对普通耐候钢SPA-C耐候性能提高约一倍。     

Accelerated lifetime measurements of P3HT:PCBM solar cells

We describe in this article the quick optimization of bulk heterojunction organic solar cells based on poly-3-hexylthiophene and [6,6]-phenyl C₆₁ butyric acid methylester blend. Best cells are found to be based on 1:1 in weight ratio and yield 3.6% power conversion efficiency under air-mass 1.5, 100 mW/cm² illumination. On the optimized cells, ageing measurements have been realized to collect the absolute values of photovoltaic parameters along the time. On this study, accelerated lifetime has been calculated using the Arrhenius model for a first-order kinetic of degradation. According to the model, we can predict a long lifetime keeping more than 80% of the initial short-circuit current density after 1000 h of working.     

FeCrAl不锈钢包壳管挤压及退火工艺优化

利用光学显微镜、扫描电镜、电子背散射衍射和万能拉伸试验机等对FeCrAl合金包壳管挤压前后的微观组织、析出相及退火后的微观组织、析出相、再结晶及力学性能进行了研究。结果表明:Nb含量对FeCrAl合金中第二相的析出影响显著,高Nb含量下Laves相的析出温度和析出数量均大大提高;降低挤压温度有助于FeCrAl合金管坯中形成细小弥散第二相;随着退火温度升高,细小弥散相的析出数量呈现先增多后减少的趋势;在相同退火工艺下,800 ℃热挤压管坯的室温力学性能比950 ℃热挤压管坯的室温力学性能要更加优异。     

中间退火处理对6016冷轧铝合金板Roping纹和组织性能的影响

利用光学显微镜和透射电镜研究了冷轧过程中间退火处理对6016铝合金表面Roping纹和组织性能的影响,测试了包边性能,观察了微观组织。结果表明:经450 ℃保温1 h的中间退火处理后,减弱了基体组织中因轧制变形形成的不同取向晶粒的条带状分布程度,弱化了基体组织不均匀屈服延伸。450 ℃的中间退火处理使得6016铝合金板材表面Roping纹完全消失,包边因子仅有0.4,包边性能最优。经350 ℃和400 ℃的中间退火处理后,表面粗晶明显,晶粒尺寸达到400~550 μm,且基体内的弥散相尺寸大、数量多,尺寸达到50~100 nm。表面粗晶和大量的晶界析出相是包边性能恶化的主要原因。     

热退火对超冶金级硅中缺陷的影响

对超冶金级硅进行不同条件下的热退火实验研究。利用金相显微镜、电子背散射衍射和X射线衍射仪分别对退火前后多晶硅不同部位的位错、晶界和择优生长取向进行表征。结果表明：退火前后多晶硅中的位错密度大小分布顺序始终是中部〈底部〈顶部。随着退火温度的升高,位错密度逐渐减小;小角度晶界不断减少,直至消失;CSL晶界比例先增加后减小。在1200℃下退火3h后,多晶硅中的孪晶晶界∑3达到28%;多晶硅上、中、下部的晶粒分别获得最佳择优生长取向,这将对后续硅材料的加工及多晶硅太阳能电池转化效率的提高起到促进作用。     

退火工艺对含铒5A06铝合金组织性能影响

对含铒5A06铝合金进行75~450℃,1h退火处理和75、150、200、250、275、300、400、470℃的从0.5~100h退火处理,并对退火后的合金进行硬度测试、光学显微镜分析、扫描电镜分析,发现退火温度对合金组织性能影响显著,退火时间对合金影响较微小。进行不同温度1h退火时,在75℃退火,合金硬度少量下降;在125~250℃温度退火,随退火温度增加合金硬度下降趋势较缓,耐腐蚀性普遍较低;在250~275℃退火后,合金硬度大幅下降,降幅达28%,但耐腐蚀性能显著提高;275℃以上温度退火,合金硬度变化趋于稳定。进行不同时间退火时,合金在小于200℃和大于275℃时硬度随时间的变化不明显,合金在任一温度下退火0.5h即可完成主要的组织性能转变,退火100与0.5h的合金组织性能差异不大,但在200~275℃区间内,随退火时间延长合金硬度连续下降,250℃退火时合金硬度随时间的延长下降最为明显。在本实验不同退火工艺下合金硬度HV均不小于850MPa。     

Enhanced boron gettering effect of n-type solar grade Si wafers by in situ oxidation

To investigate the gettering effect of n-type (phosphorous-doped) crystalline Czochralski-silicon (Cz-Si) wafers, we made boron emitters by diffusing boron into them and, subsequently, oxidized the boron-diffused n-type crystalline silicon wafers by in situ wet and dry oxidation. After oxidation, we measured the minority carrier lifetime by using microwave photoconductivity decay (μ-PCD), open-circuit voltage by quasi-steady-static photoconductance and the sheet resistance by a 4 point probe, respectively. We suggested the boron diffusion and in situ oxidation conditions to achieve longer lifetimes. We can obtain the equivalent lifetime to conventional oxidation through the quartz tube designed for boron doping and in-situ oxidation. The uniformity of sheet resistance under 3% was achieved at relatively low temperature and the lifetime of 21.6 μs was also obtained by boron gettering effect and passivation of oxide layer.