n-i-p型非晶硅太阳电池中p/ITO界面特性研究

采用射频等离子体增强化学气相沉积(RF-PECVD)技术,制备n-i-p型非晶硅(a-Si)太阳电池,采用反应热蒸发法制备ITO薄膜作为太阳电池的前电极。通过改变B2H6的掺杂浓度获得了不同晶化率的p层,详细研究了p层性能对p/ITO界面特性以及电池性能的影响。结果表明,在合适晶化率的p层上沉积ITO薄膜有利于优化p/ITO界面的接触特性,将其应用于n-i-p型a-Si太阳电池,能够显著改善电池的开路电压(Voc)和填充因子(FF),最终,在不锈钢(SS)衬底上获得了转换效率为6.57%的单结a-Si太阳电池。     

PET塑料衬底非晶/微晶硅叠层太阳电池研究

采用射频等离子体增强化学气相沉积(RF-PECVD)技术,在125℃的低温条件下,沉积了一系列不同厚度的本征微晶硅(μc-Si)薄膜。对材料的光电特性和结构特性的测试结果表明,低温条件下制备的μc-Si薄膜具有较厚的非晶孵化层,并且纵向结构演变较为明显。采用梯度H稀释技术,在沉积过程中不断降低H稀释度,改善了μc-Si薄膜的纵向均匀性。将此技术应用于非晶硅(a-Si)/μc-Si叠层电池的μc-Si底电池,在聚对苯二甲酸乙二醇酯(PET)塑料衬底上制备出初始效率达到6.0%的a-Si/μc-Si叠层电池。     

a-Si/poly-Si叠层太阳能电池的空间电荷效应和稳定性分析

基于pin结构的a-Si∶H太阳能电池中的空间电荷效应,讨论了a-Si/poly-Si叠层太阳能电池的稳定性.结果表明,在光照射下,光生空穴俘获造成了a-Si∶H中正空间电荷密度的增加,从而改变了电池内部的电场分布,提高了a-Si∶H薄膜中的电场强度.空间电荷效应不会给a-Si/poly-Si叠层结构中的a-Si∶H薄膜带来准中性区(低场"死层"),也没有发生a-Si/poly-Si叠层太阳能电池的光诱导性能衰退,因而a-Si/poly-Si叠层结构太阳能电池具有较高的稳定性.     

Al/a-Si∶H复合薄膜的电导性能

采用真空热蒸发与PECVD方法,在经特殊设计的"单反应室双沉积"设备中沉积了Al/a-Si∶H复合薄膜,并利用扫描电子显微镜、X射线衍射、Raman及X射线光电子谱等方法对复合薄膜在不同Al层厚度和不同温度退火后的晶化及电导行为进行了研究.结果表明,Al/a-Si∶H复合薄膜在不高于250℃的退火条件下即开始出现硅的晶体相.退火温度越高,Al层越厚,形成多晶硅的量越多.Al/a-Si∶H复合薄膜的电导率受Al原子在a-Si∶H中掺杂效应的影响,比纯a-Si∶H薄膜的大.随着硅晶体相在复合薄膜中的生成,复合薄膜的电导率受晶相比控制,晶相比增加,电导率增大.     

Al/a-Si∶H复合薄膜的电导性能

采用真空热蒸发与PECVD方法,在经特殊设计的"单反应室双沉积"设备中沉积了Al/a-Si∶H复合薄膜,并利用扫描电子显微镜、X射线衍射、Raman及X射线光电子谱等方法对复合薄膜在不同Al层厚度和不同温度退火后的晶化及电导行为进行了研究.结果表明,Al/a-Si∶H复合薄膜在不高于250℃的退火条件下即开始出现硅的晶体相.退火温度越高,Al层越厚,形成多晶硅的量越多.Al/a-Si∶H复合薄膜的电导率受Al原子在a-Si∶H中掺杂效应的影响,比纯a-Si∶H薄膜的大.随着硅晶体相在复合薄膜中的生成,复合薄膜的电导率受晶相比控制,晶相比增加,电导率增大.     

退火气氛对铝诱导a-Si薄膜结晶过程的影响

以玻璃为衬底,室温条件下采用直流磁控溅射技术制备了Glass/Al/a-Si样品.在H2,N2和空气3种不同气氛中进行了退火处理.分别采用XRD,Raman光谱和SEM研究了退火气氛对a-Si薄膜销诱导晶化(AIC)过程的影响.XRD实验结果表明:a-Si薄膜在H2气氛中400℃下经过90min的退火处理就能得到结晶较好的poly-si薄膜.Raman光谱实验结果表明:在500℃下退火处理,相同时间内H2气氛中a-Si结晶程度最好,空气气氛中结晶程度最差.这是因为高温H2退火过程中,高活性H原子能将弱的Si-Si键破坏,并与之反应形成强Si-Si键,使得薄膜结构更加稳定有序,同时能加速薄膜中氧的外扩散,促使薄膜晶化.     

退火气氛对铝诱导a-Si薄膜结晶过程的影响

以玻璃为衬底,室温条件下采用直流磁控溅射技术制备了Glass/Al/a-Si样品.在H2,N2和空气3种不同气氛中进行了退火处理.分别采用XRD,Raman光谱和SEM研究了退火气氛对a-Si薄膜销诱导晶化(AIC)过程的影响.XRD实验结果表明:a-Si薄膜在H2气氛中400℃下经过90min的退火处理就能得到结晶较好的poly-si薄膜.Raman光谱实验结果表明:在500℃下退火处理,相同时间内H2气氛中a-Si结晶程度最好,空气气氛中结晶程度最差.这是因为高温H2退火过程中,高活性H原子能将弱的Si-Si键破坏,并与之反应形成强Si-Si键,使得薄膜结构更加稳定有序,同时能加速薄膜中氧的外扩散,促使薄膜晶化.     

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。     

掺杂室沉积本征微晶硅材料及其在太阳能电池中的应用

在掺杂P室采用甚高频等离子体增强化学气相沉积(VHF-PECVD)技术,制备了不同硅烷浓度条件下的本征微晶硅薄膜.对薄膜电学特性和结构特性的测试结果分析表明:随硅烷浓度的增加,材料的光敏性先略微降低后提高,而晶化率的变化趋势与之相反;X射线衍射(XRD)测试表明材料具有(220)择优晶向.在P腔室中用VHF-PECVD方法制备单结微晶硅太阳能电池的i层和p层,其光电转换效率为4.7%,非晶硅/微晶硅叠层电池(底电池的p层和i层在P室沉积)的效率达8.5%.     

等离子体过程不稳定性和氢处理对HIT电池界面特性影响的研究

采用等离子体增强化学气相沉积（PECVD）技术制备薄膜硅/晶体硅异质结,通过测量沉积了本征非晶硅（a-Si:H(i)）后晶体硅（c-Si）的少子寿命以及结构为Ag/a-Si:H(p)/a-Si:H(i)/c-Si(n) /Ag 异质结的暗I-V特性,研究了等离子体初期瞬态过程和氢预处理对异质结界面性质的影响。结果表明：使用挡板且当挡板时间（tS）大于100秒时,可以有效地减少等离子体初期瞬态过程对界面性质的负面影响;与热丝化学气相沉积中氢原子处理有利于界面钝化不同,PECVD中的氢等离子体处理,由于氢原子的轰击特性,对钝化可能存在一定的不利影响;最优氢预处理时间为60秒。     

非晶硅薄膜光伏电池结构参数分析

考虑到nip型[ITO/a-Si(n)/a-Si(i)/a-Si(p)/Al]非晶硅光伏电池的各膜层厚度、掺杂浓度等因素,对非晶硅光伏电池的转换效率、填充因子、开路电压等性能参数进行了数值分析与讨论。结果表明,随p型层厚度的增加,光伏电池的短路电流密度、转换效率、开路电压值都有所增加。当本征层的厚度增加时,短波段内的光谱响应变差、内量子效率下降。当n型层厚度为5 nm,本征层厚度为5 nm,p型层厚度为10μm,受主掺杂浓度为2.5×1019cm-3,施主掺杂浓度为1.5×1016cm-3时,转换效率可达9.728%。     

Optimization of n/i and i/p buffer layers in n-i-p hydrogenated microcrystalline silicon solar cells

Hydrogenated microcrystalline silicon (μc-Si:H) intrinsic films and solar cells with n-i-p configuration were prepared by plasma enhanced chemical vapor deposition (PECVD). The influence of n/i and i/p buffer layerson the μc-Si:H cell performance was studied in detail. The experimental results demonstrated that the efficiency is much improved when there is a higher crystallinity at n/i interface and an optimized a-Si:H buffer layer at i/p interface. By combining the above methods, the performance ofμc-Si:H single-junction and a-Si:H/μc-Si:H tandemsolar ceils has been significantly improved.     

低温高速率沉积非晶硅薄膜及太阳电池

采用射频等离子体增强化学气相沉积(RF-PECVD)技术,保持沉积温度在125℃制备非晶硅薄膜材料及太阳电池。在85 Pa的低压下以及400～667 Pa的高压下,改变Si H4浓度和辉光功率等沉积参数,对本征a-Si材料的性能进行优化。结果表明,在高压下,合适的Si H4浓度和压力功率比可以使a-Si材料的光电特性得到优化,并且薄膜的沉积速率得到一定程度的提高。采用低压低速和高压高速的沉积条件,在125℃的低温条件下制备出效率为6.7%的单结a-Si电池,高压下本征层a-Si材料的沉积速率由0.06～0.08 nm/s提高到0.17～0.19 nm/s。     

High field effect mobility deuterated amorphous silicon thin-filmtransistors based on the substitution of hydrogen with deuterium

The characteristics of amorphous silicon hydrogen and deuterium thin-film transistors (a-Si:H/a-Si:D TFT) were studied. The deuterated and hydrogenated amorphous silicon channels were prepared by first annealing the as-deposited a-Si:H layer at 550°C in N₂ environment to expel all the hydrogen atoms out of the films, then the D ₂ or H₂ plasma were applied to treat the amorphous silicon layers. The field effect mobility of the conventional hydrogen TFT is usually smaller than 1 cm²/V-s. It was found that substitution of hydrogen with deuterium improved the field effect mobility of the TFT. The maximum field effect mobility of a-Si:D TFT obtained from the saturation region was 1.77 cm²/V-s     

Hydrogen dilution on an undoped silicon oxide layer and Its application to amorphous silicon thin-film solar cells

This paper proposes the use of undoped hydrogenated microcrystalline silicon oxide (μc-SiO_x:H) deposited on an n-μc-Si:H layer of amorphous silicon single-junction superstrate-configuration thin-film solar cells produced using 40 MHz very high frequency plasma-enhanced chemical vapor deposition. We found that undoped μc-SiO_x:H thin film under optimized hydrogen dilution conditions had high crystallinity, high conductivity, a wide optical band gap, and a high refractive index, which are advantageous properties in solar cells. However, deposition at higher hydrogen dilutions degraded the quality and optoelectronic properties of the films, because the morphology of the films changed from microcrystalline to amorphous. These results suggest that the use of an optimized undoped μc-SiO_x:H layer improves a-Si:H thin-film solar cell performance through enhancement of the short-circuit current density J_sc. The increased J_sc can be attributed to an improved light-trapping capability in the long wavelength range, between 620 and 680 nm, as demonstrated by the external quantum efficiency. This technique also allows optimal conversion efficiency to be achieved. The results demonstrated that hydrogen dilution plays a dominant role in the improvement of film quality and solar cell performance; however, the tradeoff between refractive index and conductivity must be considered.     

Performance of bifacial HIT solar cells on n-type silicon substrates

The performance of amorphous silicon(a-Si:H) /crystalline silicon(c-Si) heterojunction is studied,and the effects of the emitter layer thickness,doping concentration,intrinsic layer thickness,back heavily-doped n layer,interface state and band offset on the optical and electrical performance of bifacial heterojunction with intrinsic thin-layer(HIT) solar cells on ntype silicon substrates are discussed.It is found that the HIT solar cells on n-type substrates can obtain a higher conversion efficiency than th...     

Understanding the Effects of Stress on the Crystallization of Amorphous Silicon

This paper presents the results of a systematic study on the effects of stress on aluminum-induced crystallization (AIC) of plasma-enhanced chemical-vapor-deposited (PECVD) amorphous silicon (a-Si:H). To decouple the impact of stress on the AIC of a-Si:H from other factors that may affect crystallization, such as a-Si:H and aluminum deposition conditions, identical thin film structures [Al (200 nm)/a-Si:H (200 nm)] were deposited on the front surface of all samples. On the back surfaces, various amorphous silicon films were deposited to adjust the curvature of the samples and, therefore, the stress in the a-Si:H film on the front surface. It was found that tensile stress in a-Si:H can retard the AIC of a-Si:H.     

Flexible a-Si:H Position-Sensitive Detectors

Flexible and large area (5 mm /spl times/80 mm with an active length of 70 mm) position-sensitive detectors (PSDs) deposited onto polymeric substrates (polyimide-Kapton VN) have been fabricated. The optimized structure presented is based on a heterojunction of amorphous silicon (a-Si:H)/ZnO:Al. The sensors were characterized by spectral response, photocurrent dependence as a function of light intensity, and position detection measurements. The set of data obtained on one-dimensional PSDs based on the heterojunction show excellent performances with a maximum spectral response of 0.12 A/W at 500 nm and a nonlinearity of /spl plusmn/10% over 70-mm length. The produced sensors present a nonlinearity higher than those ones produced on glass substrates, due to the different thermal coefficients exhibited by the polymer and the a-Si:H film. In order to prove this behavior, it was measured the defect density obtained by the constant photocurrent method on a-Si:H thin films deposited on polymeric substrates and bent with different radii of curvature.     

Ion implanted contacts to a-Si:H thin-film transistors

Fabrication steps to improve ion implanted source-drain contacts to hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFT's) have been determined. After establishing a contact performance baseline using devices made with Al/intrinsic a-Si:H contacts, improvements were made to the metal/a-Si:H contact scheme using unheated and heated implants, single- and double-level phosphorous implants, a buffered HF acid dip just prior to metal deposition, Al and Al-Si-Cu metallization schemes, and a post-metallization anneal.     

柔性衬底硅基太阳电池ZAO透明导电膜的研究

采用孪生对靶直流磁控溅射的方法,在室温下制备了ZnO:Al(ZAO)薄膜材料,将其应用于柔性衬底非晶硅薄膜太阳电池的窗口电极。通过调整Ar气流量(1.67×10-7 m3/s～8.33×10-7 m3/s),优化了ZAO薄膜的结构、成份及光电性能。得到如下结论:理想的Ar气流量为3.33×10-7 m3/s,此时ZAO薄膜具有较高的晶化率和C轴择优取向,薄膜的霍尔电阻率达为4.26×10-4Ω.cm,载流子浓度达到1.8×1021cm-3,可见光波长范围内的光学透过率达到85%以上。将优化后的ZAO薄膜用于柔性衬底非晶硅薄膜太阳电池的窗口电极,转化效率达到了4.26%。