Improvement in IBC-silicon solar cell performance by insertion of highly doped crystalline layer at heterojunction interfaces

By inserting a thin highly doped crystalline silicon layer between the base region and amorphous silicon layer in an interdigitated back-contact （IBC） silicon solar cell, a new passivation layer is investigated. The passivation layer performance is characterized by numerical simulations. Moreover, the dependence of the output parameters of the solar cell on the additional layer parameters （doping concentration and thickness） is studied. By optimizing the additional passivation layer in terms of doping concentration and thickness, the power conversion efficiency could be improved by a factor of 2.5%, open circuit voltage is increased by 30 mV and the fill factor of the solar cell by 7.4%. The performance enhancement is achieved due to the decrease of recombination rate, a decrease in solar cell resistivity and improvement of field effect passivation at heterojunction interface. The above-mentioned results are compared with reported results of the same conventional interdigitated back-contact silicon solar cell structure. Furthermore, the effect of a-Si：H/c-Si interface defect density on IBC silicon solar cell parameters with a new passivation layer is studied. The additional passivation layer also reduces the sensitivity of output parameter of solar cell to interface defect density.

Surface morphology and impurity distribution of electron beam recrystallized silicon films on low cost substrates for solar cell absorber

A line shaped electron beam recrystallised polycrystalline silicon film on the low cost substrate was investigated for the use of the solar cell absorber. The applied EB energy density strongly influences the surface morphology of the film system. Lower EB energy density results in droplet morphology and the rougher SiO2 capping layer due to the low fluidity. With the energy increasing, the capping layer becomes smooth and continuous and less and small pinholes form in the silicon film. Tungstendisilicide (WSi2) is formed at the interface tungsten/silicon but also at the grain boundaries of the silicon. Because of the fast melting and cooling of the silicon film, the eutectic of silicon and tungstendisilicide mainly forms at the grain boundary of the primary silicon dendrites. The SEM-EDX analysis shows that there are no chlorine and hydrogen in the area surrounding a pinhole after recrystallization because of outgassing during the solidification.

Back Surface Recombination Velocity Dependent of Absorption Coefficient as Applied to Determine Base Optimum Thickness of an n+/p/p+ Silicon Solar Cell

The monochromatic absorption coefficient of silicon, inducing the light penetration depth into the base of the solar cell, is used to determine the optimum thickness necessary for the production of a large photocurrent. The absorption-generation-diffusion and recombination (bulk and surface) phenomena are taken into account in the excess minority carrier continuity equation. The solution of this equation gives the photocurrent according to absorption and electronic parameters. Then from the obtained short circuit photocurrent expression, excess minority carrier back surface recombination velocity is determined, function of the monochromatic absorption coefficient at a given wavelength. This latter plotted versus base thickness yields the optimum thickness of an n+-p-p+ solar cell, for each wavelength, which is in the range close to the energy band gap of the silicon material. This study provides a tool for improvement solar cell manufacture processes, through the mathematical relationship obtained from the thickness limit according to the absorption coefficient that allows base width optimization.

Influence of Both Magnetic Field and Temperature on Silicon Solar Cell Base Optimum Thickness Determination

The minority carrier’s recombination velocity at the junction and at the back surface is used for the modeling and determination of the optimum thickness of the base of a silicon solar cell in the static regime, under magnetic field and temperature influence. This study takes into account the Umklapp process and the Lorentz effect on the minority carriers photogenerated in the base.

AC Back Surface Recombination Velocity in n⁺-p-p⁺Silicon Solar Cell under Monochromatic Light and Temperature

Excess minority carrier’s diffusion equation in the base of monofaciale silicon solar cell under frequency modulation of monochromatic illumination is resolved. Using conditions at the base limits involving recombination velocities Sf and Sb, respectively at the junction (n+/p) and back surface (p+/p), the AC expression of the excess minority carriers’ density δ (T, ω) is determined. The AC density of photocurrent Jph (T, ω) is represented versus recombination velocity at the junction for different values of the temperature. The expression of the AC back surface recombination velocity Sb of minority carriers is deduced depending on the frequency of modulation, temperature, the electronic parameters (D (ω)) and the thickness of the base. Bode and Nyquist diagrams are used to analyze it.

Junction Surface Recombination Concept as Applied to Silicon Solar Cell Maximum Power Point Determination Using Matlab/Simulink: Effect of Temperature

In this work, we study the method for determining the maximum of the minority carrier recombination velocity at the junction Sfmax, corresponding to the maximum power delivered by the photovoltaic generator. For this, we study the temperature influence on the behavior of the front white biased solar cell in steady state. By solving the continuity equation of excess minority carrier in the base, we have established the expressions of the photocurrent density, the recombination velocity on the back side of the base Sb, and the photovoltage. The photocurrent density and the photovoltage are plotted as a function of Sf, called, minority carrier recombination velocity at the junction surface, for different temperature values. The illuminated I-V characteristic curves of the solar cell are then derived. To better characterize the solar cell, we study the electrical power delivered by the base of the solar cell to the external charge circuit as either junction surface recombination velocity or photovoltage dependent. From the output power versus junction surface recombination velocity Sf, we have deduced an eigenvalue equation depending on junction recombination velocity. This equation allows to obtain the maximum junction recombination velocity Sfmax corresponding to the maximum power delivered by the photovoltaic generator, throughout simulink model. Finally, we deduce the conversion efficiency of the solar cell.

Back Surface Recombination Velocity Modeling in White Biased Silicon Solar Cell under Steady State

In this paper, we extend the concept of back surface recombination through a study of a silicon mono facial solar cell in static regime and under polychromatic illumination. Back surface recombination velocities noted Sbe, Sbj and Sbr are determined for which respectively we derived, the power, the fill factor and the conversion efficiency, that become constant whatever the thickness of the solar cell. We have then obtained the expression of the minority carrier’s density in the base from the continuity equation. We then have determined the photocurrent density, the photo voltage, the power, the fill factor and finally the conversion efficiency.

Surface Recombination Concept as Applied to Determinate Silicon Solar Cell Base Optimum Thickness with Doping Level Effect

New expressions of back surface recombination of excess minority carriers in the base of silicon solar are expressed dependent on both, the thickness and the diffusion coefficient which is in relationship with the doping rate. The optimum thickness thus obtained from the base of the solar cell allows the saving of the amount of material needed in its manufacture without reducing its efficiency.

n⁺-p-p⁺Silicon Solar Cell Base Optimum Thickness Determination under Magnetic Field

Base optimum thickness is determined for a front illuminated bifacial silicon solar cell n+-p-p+ under magnetic field. From the magneto transport equation relative to excess minority carriers in the base, with specific boundary conditions, the photocurrent is obtained. From this result the expressions of the carrier’s recombination velocity at the back surface are deducted. These new expressions of recombination velocity are plotted according to the depth of the base, to deduce the optimum thickness, which will allow the production, of a high short-circuit photocurrent. Calibration relationships of optimum thickness versus magnetic field were presented according to study ranges. It is found that, applied magnetic field imposes a weak thickness material for solar cell manufacturing leading to high short-circuit current.

多晶硅太阳电池表面化学织构工艺

用化学腐蚀方法织构多晶硅片的表面 ,利用SEM分析了化学腐蚀后多晶硅片表面状态 ,通过反射谱的测试 ,分析了多晶硅片表面陷光效果。结果表明酸溶液腐蚀的硅片表面相对平整 ,有均匀的腐蚀坑 ,反射率很小。在没有任何减反射膜的情况下 ,在 5 0 0～ 10 0 0nm波长范围内 ,反射率在 16%以下 ,有较好的表面陷光效果。而用碱溶液和双织构腐蚀方法得到的多晶硅表面陷光作用都不很理想 ,反射率高于酸溶液腐蚀硅片 。

晶硅太阳电池上表面减反射膜的效果评价与分析

本文首先利用Silvaco-TCAD半导体器件仿真软件建立基于优化减反射膜结构的二维晶硅太阳电池结构。然后利用传递矩阵法（TMM）,优化设计由多种常见介质膜材料组成的减反射膜结构。最后详细分析了Si O2/Si3N4和Mg F2/Zn S双层减反射膜对太阳电池性能的影响。结果表明：在400-750 nm波长范围内,Mg F2/Zn S减反射膜光反射损耗最小。在850-1200 nm波长范围内,Si O2/Si3N4减反射膜光反射损耗最小。光反射损耗越小,太阳电池量子效率和转换效率越高。减反射膜的钝化效果对晶硅电池短波段（λ〈550 nm）光谱响应影响较大。通过光吸收效果和钝化效果对减反射膜性能进行综合评价,Si O2/Si3N4减反射膜优于Mg F2/Zn S减反膜,更有利于晶硅太阳电池转换效率的提高。

多晶硅太阳电池的表面和界面复合

根据晶格的周期性排列中断而在边界产生悬挂键理论 ,分析了多晶硅太阳电池的表面和界面复合问题 ,指出对表面和界面进行钝化和建立合适的表面和界面场是降低表面和界面对光生少数载流子的复合速度 ,从而降低表面和界面复合电流 ,提高光电流输出的重要方法。

酸腐多晶硅太阳电池表面织构的研究

多晶硅太阳电池是目前光伏发展的主要趋势,而缺乏有效的表面织构的方法是多晶硅太阳电池发展的一个瓶颈。采用酸腐多晶硅片的方法获得各向同性的表面织构。酸腐蚀液选取HF-HNO3混合溶液并用H2SO4进行改良。分别利用扫描电镜(SEM)和光谱响应系统分析了腐蚀后多晶硅片的表面形貌和反射率。结果表明,酸腐多晶硅表面分布均匀的蠕虫状腐蚀坑,反射率很低,在PECVDSiNx减反射膜后反射率大大下降。

热氧化生长的SiO_2钝化膜对晶体硅太阳电池性能的影响

使用干氧热氧化的方法在晶体硅太阳电池表面生长SiO2钝化膜。结果表明:在780℃下生长的氧化薄膜钝化效果较好,实验检测少子寿命提高了8.3μs,以此为基础制备的太阳电池转换效率达到17.38%。实验还对氮气气氛下的氧化进行研究,发现当氮气流量为10L/min时,能强化薄膜的钝化效果,少子寿命可提高9.4μs。

基于负性光刻胶掩膜的湿法多晶硅制绒

提出了一种用于大规模多晶硅太阳能电池生产的制绒工艺,采用负性光刻胶作为湿法刻蚀的掩膜,制备蜂巢状低反射率绒面。通过研究氢氟酸/硝酸溶液中各向同性刻蚀时腐蚀坑的形成过程,发现随着刻蚀时间的增加,在掩膜图形的开孔下逐渐形成六方分布的球面形状的腐蚀坑,腐蚀坑的深径比(深度/开孔直径)出现先上升然后下降的趋势。同理论计算值对比发现,随着刻蚀时间增加,掩膜和硅片的附着紧密性及掩膜的阻挡效应降低,酸液可能渗入了掩膜和硅片的界面,横向刻蚀速度快速上升,降低了深径比,导致实际的反射率高于理论计算值。尽管如此,本文还是成功制备了孔径15微米的蜂巢状绒面,反射率达到了22.9%。

低效纳米孔晶体硅太阳电池性能研究

晶体硅太阳电池生产中,降低表面反射率能够提高太阳电池短路电流和转换效率.纳米孔硅的表面反射率极低,但报道中所实现的太阳电池输出参数(开路电压、短路电流、填充因子)都低于金字塔结构表面.采用对比法从光学性能、表面微结构和电极接触上对纳米孔硅和金字塔太阳电池进行比较分析,来研究纳米多孔硅太阳电池转换效率的抑制因素.研究表明短时间腐蚀的纳米孔硅太阳电池表面沉积氮化硅钝化膜后的平均反射率提高.长时间腐蚀的纳米孔硅表面沉积氮化硅后在短波段的反射率极低,因此平均反射率小于金字塔结构表面.但是由于纳米孔硅太阳电池的表面复合率高,而孔壁上附着的毛刺不仅会进一步增大表面复合,还会削弱表面钝化效果,因此短波段激发的光生载流子难以被太阳电池利用.所以,光利用和表面复合是抑制纳米孔硅太阳电池开路电压和短路电流的原因,而过大的串联电阻是纳米孔硅太阳电池短路电流和填充因子低的另一个原因.

硼镓共掺多晶硅背钝化太阳电池的光衰研究

研究同一小硅锭中不同部位的硼镓共掺多晶硅片制备成背钝化太阳电池后,不同的电池效率和光衰情况,并研究经过同样的抗光衰处理后这些电池的光衰情况。测试结果显示,硅锭尾部位置的硅片具有最高的电阻率、最高的氧含量、最低的硼、镓含量及最高的杂质含量。将硅锭不同位置的硅片经过量产产线制成背钝化电池后,头部硅片得到的电池片的平均转换效率为19.08%,中部硅片得到的电池片的平均转换效率平均效率为19.15%,尾部硅片得到的电池片的平均转换效率为19.06%。光衰结果显示,对于未经过抗光衰处理的电池片,头部和中部位置具有较低的光衰比例,而尾部位置具有较高的光衰比例;电池片经过抗光衰处理后,不同位置对应的电池片都有效率提升,继续经过光衰测试后,尾部位置出现较明显的抗光衰效果。该研究对硼镓共掺多晶硅片生产和多晶背钝化电池抗光衰工艺具有指导意义。

H_(2)O和O_(3)对热原子层沉积Al_(2)O_(3)薄膜性能研究

采用热原子层沉积的方法,以三甲基铝(TMA)为铝源,配合H_(2)O、O_(3)及H_(2)O+O_(3)这3种不同的氧化剂制备Al_(2)O_(3)薄膜并研究Al_(2)O_(3)薄膜的生长、元素分布、薄膜结构和表面钝化质量随氧化剂种类和后退火工艺的变化规律。结果表明,H_(2)O基的Al_(2)O_(3)薄膜具有较高的沉积速率及薄膜折射率,同时具有较低的杂质元素浓度和界面态缺陷密度;O_(3)基的Al_(2)O_(3)薄膜则具有较高的固定负电荷密度和较好的热稳定性。通过在O_(3)工艺中加入H_(2)O,可有效降低Al_(2)O_(3)薄膜中杂质元素浓度和界面缺陷态密度,同时保留O_(3)基Al_(2)O_(3)薄膜中较高的固定负电荷密度,从而在钝化性能上兼具两者的优势。

利用金属辅助化学腐蚀法在硅表面获得纳米绒面结构以提升多晶硅太阳电池效率

在硅片表面制备绒面结构能够有效降低太阳光在硅片表面的反射损失，是提高太阳能电池转换效率的一条重要途径。通过真空热蒸发法在多晶硅片上沉积纳米银颗粒，利用金属辅助化学腐蚀（MACE）法，制备了不同腐蚀时间下的纳米绒面结构，其中，腐蚀时间为60 s 的纳米绒面的平均反射率低至4.66%（300～1100 nm）。同时，对腐蚀时间为60 s的纳米绒面用KOH 溶液进行优化处理，将KOH 处理前后的多晶硅片采用常规电池工艺进行电池制备研究。对比发现，经过KOH 处理后的电池效率比未经KOH 处理的电池效率提高了0.43%。

等离激元共振增强多晶硅薄膜太阳电池性能研究

采用磁控溅射方法,在多晶硅薄膜太阳电池表面沉积了不同粒径大小的Au纳米粒子,利用粒径大小可调控的Au纳米粒子的局域表面等离激元共振增强效应(LSPR),对入射光中的可见光区域实现"光俘获";采用UV-vis吸收光谱对LSPR进行了研究,结果表明,LSPR能够有效拓展Au纳米粒子的光谱响应范围(400~800nm),并且,随着Au纳米粒子粒径的增大,LSPR共振吸收峰呈现出明显"红移";同时,通过SERS表征,证实LSPR能够有效增强Au纳米粒子周围的局域电磁场强度;最后,多晶硅太阳电池的J-V特性曲线表明,当Au纳米粒子溅射时间为50s时,多晶硅太阳电池光电转换效率(η)最高为14.8%,比未修饰Au纳米粒子的电池η提高了42.3%。