嵌入a-Si:H薄层的μc-Si/c-Si pn异质结太阳能电池热平衡态特性的数值模拟分析

应用计算机数值模拟方法计算p+(μc-Si:H)/n(c-Si)及p+(μc-Si:H)/i(a-Si:H)/n(c-Si)异质结太阳能电池中的电场强度分布,说明μc-Si/c-Si异质结电池制造中μc-Si:H膜厚选择,进而对嵌入a-Si:H薄层的μc-Si/c-Si异质结太阳能电池设计进行分析,包括a-Si:H薄层p型掺杂效应及本底单晶硅的电阻率选择,最后讨论μc-Si/c-Si异质结太阳能电池稳定性.     

β-FeSi2(n)/a-Si(i)/c-Si(p)/μc-Si(p+)异质结太阳能电池模拟与优化

运用AFORS-HET软件对β-FeSi2(n)/a-Si(i)/c-Si(p)/μc-Si(p+) HIT型异质结太阳能电池的性能进行了模拟,并对各层参数进行了优化。模拟结果表明,在FeSi2(n) /c-Si(p)结构上加上本征层和背场,能显著地提高电池的性能。加入缺陷并优化各项参数后,电池的最后参数为VOC=647.7 mV, JSC=42.29 mA·cm-2, FF=75.32%, EFF=20.63%, β-FeSi2(n) /c-Si(p)太阳能电池的效率提高了2.3%。     

(p)nc-Si:H/(n)c-Si异质结变容二极管

采用等离子体增强化学气相沉积技术和电子束蒸发技术制备了一种新型的线性缓变异质结变容二极管--Au/Cr合金(电极)/multi-layer(p)nc-Si:H/(n)c-Si/(电极)Au/Ge合金结构.I-V,C-V,G-f以及DLTS的测试结果表明:其电容变化系数远大于单晶硅线性缓变异质结的电容变化系数,正向导电机制符合隧穿辅助辐射-复合模型,这是nc-Si:H层中nc-Si晶粒的量子效应所致;反向电流主要由异质结中空间电荷区的产生电流决定,且反向漏电流小,反向击穿电压高,表现出较好的整流特性.     

嵌入a-Si∶H薄层的μc-Si/c-Sipn异质结太阳能电池热平衡态特性的数值模拟分析

应用计算机数值模拟方法计算ｐ＋ （μｃ－Ｓｉ∶Ｈ） ／ｎ （ｃ－Ｓｉ） 及ｐ＋ （μｃ－Ｓｉ∶Ｈ） ／ｉ （ａ－Ｓｉ∶Ｈ） ／ｎ （ｃ－Ｓｉ） 异质结太阳能电池中的电场强度分布, 说明μｃ－Ｓｉ／ｃ－Ｓｉ异质结电池制造中μｃ－Ｓｉ∶Ｈ 膜厚选择,进而对嵌入ａ－Ｓｉ∶Ｈ 薄层的μｃ－Ｓｉ／ｃ－Ｓｉ异质结太阳能电池设计进行分析, 包括ａ－Ｓｉ∶Ｈ 薄层ｐ 型掺杂效应及本底单晶硅的电阻率选择, 最后讨论μｃ－Ｓｉ／ｃ－Ｓｉ异质结太阳能电池稳定性     

基于P3HT/PCBM异质结界面太阳能电池的理论及实验研究

根据整数电荷转移(ICT)模型理论分析基于P3HT为给体PCBM为受体的异质结界面,认为不同等效功函数衬底和电荷传输状态产生不同D/A界面特性。采用增加P3HT缓冲层PCBM缓冲层的方法,制备不同复合层本体异质结结构光伏器件,研究活性膜内组分变化对器件开路电压和短路电流密度的影响。结果表明增加缓冲层使器件的短路电流密度明显提高,从3.96mA/cm2分别增加到4.51mA/cm2和4.70mA/cm2,但对开路电压影响不大。     

双应变SiGe/Si异质结CMOS的设计及其电学特性的Medici模拟

本文提出一种沟道长度为0.125 μm的异质结CMOS(HCMOS)器件结构.在该结构中,压应变的SiGe与张应变的Si分别作为异质结PMOS(HPMOS)与异质结NMOS(HNMOS)的沟道材料,且HPMOS与HNMOS为垂直层叠结构;为了精确地模拟该器件的电学特性,修正了应变SiGe与应变Si的空穴与电子的迁移率模型;利用Medici软件对该器件的直流与交流特性,以及输入输出特性进行了模拟与分析.模拟结果表明,相对于体Si CMOS器件,该器件具有更好的电学特性,正确的逻辑功能,且具有更短的延迟时间,同时,采用垂直层叠的结构此类器件还可节省约50%的版图面积,有利于电路的进一步集成.     

纳米硅/晶体硅异质结电池的暗I-V特性和输运机制

采用HWCVD技术在P型CZ晶体硅衬底上制备了纳米硅／晶体硅异质结太阳电池,测量了晶体硅表面在不同氢处理时间下的异质结的暗I-V特性和相应的电池性能参数．室温下的正向暗I-V特性采用双二极管模型来拟合,可将0～1V的电压范围区分为4个区域：旁路电阻（0～0．15V）、非理想二极管2（0．15～0．3V）、理想二极管1（0．3～0．5V）和串联电阻（〉0．5V）．拟合结果表明,适当的氖处理时间（～30s）可有效降低非理想二极管的理想因子n2,即降低界面复合电流,表明具有好的界面特性．对于282～335K的暗I—V温度特性的研究表明,在0．15～0．3V的低电压范围,暗电流主要由耗尽区的复合电流提供,0．3～0．5V电压范围,对输运起主要作用的是隧穿过程,该过程可用通过界面陷阱能级的隧穿模型来解释．     

纳米硅/晶体硅异质结电池的暗Ⅰ-Ⅴ特性和输运机制

采用HWCVD技术在p型CZ晶体硅衬底上制备了纳米硅/晶体硅异质结太阳电池,测量了晶体硅表面在不同氢处理时间下的异质结的暗Ⅰ-Ⅴ特性和相应的电池性能参数.室温下的正向暗Ⅰ-Ⅴ特性采用双二极管模型来拟合,可将0～1V的电压范围区分为4个区域:旁路电阻(0～0.15V)、非理想二极管2(0.15～0.3V)、理想二极管1(0.3～0.5V)和串联电阻(>0.5V).拟合结果表明,适当的氢处理时间(～30s)可有效降低非理想二极管的理想因子n2,即降低界面复合电流,表明具有好的界面特性.对于282～335K的暗Ⅰ-Ⅴ温度特性的研究表明,在0.15～0.3V的低电压范围,暗电流主要由耗尽区的复合电流提供,0.3～0.5V电压范围,对输运起主要作用的是隧穿过程,该过程可用通过界面陷阱能级的隧穿模型来解释.     

纳米硅/晶体硅异质结电池的暗Ⅰ-Ⅴ特性和输运机制

采用HWCVD技术在p型CZ晶体硅衬底上制备了纳米硅/晶体硅异质结太阳电池,测量了晶体硅表面在不同氢处理时间下的异质结的暗Ⅰ-Ⅴ特性和相应的电池性能参数.室温下的正向暗Ⅰ-Ⅴ特性采用双二极管模型来拟合,可将0～1V的电压范围区分为4个区域:旁路电阻(0～0.15V)、非理想二极管2(0.15～0.3V)、理想二极管1(0.3～0.5V)和串联电阻(>0.5V).拟合结果表明,适当的氢处理时间(～30s)可有效降低非理想二极管的理想因子n2,即降低界面复合电流,表明具有好的界面特性.对于282～335K的暗Ⅰ-Ⅴ温度特性的研究表明,在0.15～0.3V的低电压范围,暗电流主要由耗尽区的复合电流提供,0.3～0.5V电压范围,对输运起主要作用的是隧穿过程,该过程可用通过界面陷阱能级的隧穿模型来解释.     

Adaptation of admittance analysis to extract interface traps of a-Si:H/c-Si heterojunctions

Complete admittance expressions, adapted from the equations previously presented for Metal/Oxide/Semiconductor (MOS) structure, were derived and modified admittance approach was successfully applied on a-Si:H/c-Si heterojunction to deduce surface state density (N_ss) by employing capacitance–voltage (C–V) and conductance–voltage (G/ω–V) measurements. Through the approach, N_ss was determined as 6×10¹² cm⁻² eV⁻¹ that was mutually checked by continuum model, used previously for evaluating N_ss in MOS structure. Furthermore, locating such an amount at the interface of a-Si:H and c-Si, experimentally measured C–V curve was reproduced through AFORS-HET simulation program. Presence of such a large amount of N_ss was originated due to native oxide layer, confirmed through spectroscopic elipsometry measurement.     

异质结硅太阳能电池a—Si：H薄膜的研究

通过应用Scharfetter-Gummel数值求解Poisson方程，对热平衡态P^ （a-Si:H)/n(c-Si)异质结太阳能电池进行计算机数值模拟分析。结果指出，采用更薄P^ (a-Si：H）薄膜设计能有效增强光生载流子的传输与收集，从而提高a-Si/c-Si异质结太阳能电池的性能。同时，还讨论了P^ (a-Si:h)薄膜中P型掺杂浓度对光生载流了传输与收集的影响。高强茺光照射下模拟，计算表明，a-Si/c-Si异质结结构太阳能电池具有较高光稳定性。     

a-Si/c-Si异质结结构太阳能电池设计分析

通过应用 Scharfetter- Gum mel解法数值求解 Poisson方程 ,对热平衡态 a- Si/ c- Si异质结太阳能电池进行计算机数值模拟分析 ,着重阐述在 a- Si/ c- Si异质结太阳能电池中嵌入 i( a- Si:H)缓冲薄层的作用 ,指出采用嵌入 i( a- Si:H )缓冲薄层设计能有效增强光生载流子的传输与收集 ,从而提高 a- Si/ c- Si异质结太阳能电池的性能 ,同时还讨论 p+ ( a- Si:H)薄膜厚度和 p型掺杂浓度对光生载流子传输与收集的影响 ,而高强度光照射下模拟计算表明 ,a- Si/ c- Si异质结结构太阳能电池具有较高光稳定性     

Numerical simulation of the effect of the free carrier motilities on light-soaked a-Si:H p-i-n solar cell

Using a previous model, which was developed to describe the light-induced creation of the defect density in the a-Si:H gap states, we present in this work a computer simulation of the a-Si:H p-i-n solar cell behavior under continuous illumination. We have considered the simple case of a monochromatic light beam nonuniformly absorbed. As a consequence of this light-absorption profile, the increase of the dangling bond density is assumed to be inhomogeneous over the intrinsic layer (i-layer). We investigate the internal variable profiles during illumination to understand in more detail the changes resulting from the light-induced degradation effect. Changes in the cell external parameters including the open circuit voltage, V_oc, the short circuit current density, J_sc, the fill factor, FF, and the maximum power density, P_max, are also presented. This shows, in addition, the free carrier mobility influence. The obtained results show that V_oc seems to be the less affected parameter by the light-induced increase of the dangling bond density. Moreover, its degradation is very weak-sensitive to the free carrier mobility. Finally, the free hole mobility effect is found to be more important than that of electrons in the improvement of the solar cell performance.     

掺杂B(CH)3的P型a-SiC:H层及a-Si:H电池的P/I界面研究

研究了衬底温度、反应气体流量等工艺条件对掺杂B(CH3)3(TMB)的P型氢化非晶硅碳(a-SiC:H)窗口材料性能的影响,获得了电导率达到8.97×10-7 S/cm、光学带隙大于2.0 eV的P型a-SiC:H窗口材料.研究了单结电池P型a-SiC:H窗口层的CH4流量与P、I层制备温度三者间的匹配关系.结果表明,随着衬底温度的提高,需要更多的CH4流量以增大P型窗口层的带隙Eg和电池的短路电流密度Jsc;沉积系统中,P型窗口层的温度比本征吸收层高25～50 ℃时,电池性能较好.研究了3种类型的P/I缓冲层对单结电池性能的影响.大量实验表明,不掺B的C缓冲层适合于低温和小CH4流量情况使用;掺B的C缓冲层 不掺B的C缓冲层适合于高温和大CH4流量情况使用;采用不掺B的C缓冲层的电池光稳定性高于采用B、C渐变缓冲层的电池.研究还表明,采用新型TMB作为P型窗口层掺杂剂的电池比传统采用B2H6作为P型窗口层掺杂剂的电池转换效率提高约1.0%.     

Al/a-Si:H界面反应和热处理行为光发射研究

利用XPS和AES对Al/a-Si∶H界面进行了研究.实验结果表明,最初阶段Al淀积在a-Si∶H上出现金属团.Al淀积量超过一定值后,起化学反应的Al和Si形成了互溶区,同时没有化学反应的Al在表面上形成金属Al层.此外,真空热处理加剧了Al/aSi∶H的界面反应和元素互扩散.     

Simulation analysis of the DC current gain in an n-p-n a-Si:H/SiGe/Si heterojunction bipolar transistor

This paper presents the results of a simulation study focused on the evaluation of the DC characteristics of an n-p-n SiGe-based heterojunction bipolar transistor (HBT) performing an extremely thin n⁺ hydrogenated amorphous silicon (a-Si:H) emitter. The a-Si:H(n)/SiGe(p) structure exhibits an energy gap difference of approximately 0.8 eV mostly located at the valence band side and this results in an optimal configuration for the emitter/base junction to improve the emitter injection efficiency and thus the device performance.Considering a 20% Ge uniform concentration profile in the base region, simulations indicate that the DC characteristics of an a-Si:H/SiGe HBT are strictly dependent on two essential geometrical parameters, namely the emitter width and the base width. In particular, the emitter thickness degrades device characteristics in terms of current handling capabilities whereas higher current gains are obtained for progressively thinner base regions. A DC current gain exceeding 9000 can be predicted for an optimized device with a thin emitter and a 10 nm-thick, doped base.     

First-principles study on electronic properties and lattice structures of WZ-ZnO/CdS interface

We theoretically investigated the lattice structure, interface bonding energy, optical absorption properties and electronic properties of WZ-ZnO (1 1 2)/CdS (1 1 0) interface from first-principles calculations. The interface lattice mismatch is less than 4.3%. The atomic bond lengths and atomic positions change slightly on the interface after relaxation. The WZ-ZnO (1 1 2)/CdS (1 1 0) interface has bonding energy about −0.61 J/m², suggesting that this interface can exist stably. Through analysis of the density of states, no interface state is found near the Fermi level. In addition, there are orbital hybridizations between different interfacial atoms, and these orbital hybridizations effectively enhance the bonding of Zn and S atoms, Cd and O atoms on the interface. By analysis of difference density charge and Bader charge, we find that electrons on the interface are largely redistributed and charges transport near the Fermi level which strengthen the adhesion of the interface.     

Investigation of Co/SiC interface reaction

Interface reaction, phase transition, and composition were investigated for Co thin films on amorphous SiC films as a function of heat treatment (600～1000°C). Amorphous SiC layers were grown on (001) Si substrate by magnetron sputter deposition. The SiC layers had a 1:1 stoichiometric ratio of Si to C and an amorphous structure containing microcrystals. The interface reaction between a sputter-deposited Co (250Å thick) and amorphous SiC (2000Å thick) layer on a (001) Si substrate induced by vacuum annealing at temperatures of 600–1000°C was examined. Co₂Si was formed at 700°C as the first crystalline phase and CoSi at 800°C as the final stable phase of the Co/SiC interface reaction. This phase sequence of Co₂Si→CoSi was interpreted in terms of the effective heat of formation and the calculated ternary Co-Si-C phase diagram, and it was consistent with the experimental results. The high formation temperature of the first crystalline Co₂Si phase and no formation of a final stable CoSi₂ phase are discussed in comparison with Co/Si interface reaction and related to the binding energy of the reacting materials. In addition, the behavior of free carbon remaining after the Co/SiC reaction was investigated. This free carbon moved to the top of the reacted cobalt silicide/SiC layer.