原子层沉积氧化铝薄膜对多晶太阳能电池表面钝化的影响

A stack of Al2O3/SiNx dual layer was applied for the back side surface passivation of p-type multi-crystalline silicon solar cells, with laser-opened line metal contacts, forming a local aluminum back surface field （local Al-BSF） structure. A slight amount of Al2O3, wrapping around to the front side of the wafer during the thermal atomic layer deposition process, was found to have a negative influence on cell performance. The different process flow was found to lead to a different cell performance, because of the Al2O3 wrapping around the front surface. The best cell performance, with an absolute efficiency gain of about 0.6% compared with the normal full Al-BSF structure solar cell, was achieved when the Al2O3 layer was deposited after the front surface of the wafer had been covered by a SiNx layer. We discuss the possible reasons for this phenomenon, and propose three explanations as the Ag paste, being hindered from firing through the front passivation layer, degraded the SiNx passivation effect and the Al2O3 induced an inversion effect on the front surface. Characterization methods like internal quantum efficiency and contact resistance scanning were used to assist our understanding of the underlying mechanisms.     

PEALD制备的Al2O3薄膜在n-TOPCon太阳电池上的钝化性能

对采用等离子体增强原子层沉积(PEALD)法制备的Al2O3薄膜在n型单晶硅隧穿氧化层钝化接触(TOPCon)太阳电池正表面的钝化性能进行了研究.采用少数载流子寿命、X射线电子能谱(XPS)及J-V特性的测试分析,重点研究了 Al2O3沉积温度、薄膜厚度及薄膜形成后不同退火条件对钝化性能的影响,实现了低表面复合速率、良好钝化效果的产业化制备的Al2O3薄膜工艺.研究结果表明,在沉积温度为150℃、膜厚为5 nm、退火温度为450℃时,测试计算得出薄膜中O和Al的原子数之比为2.08,电池发射极正表面复合速率较低,达到了Al2O3钝化的最优效果,并且分析了 Al2O3薄膜的化学态和形成机理.利用其Al2O3薄膜工艺制备的n型单晶硅TOPCon太阳电池开路电压提升了 8 mV,电池的平均光电转换效率达到了 23.30％.     

溅射条件对Al2O3薄膜介电强度和沉积速率的影响

用射频溅射方法，在不同工作气体（纯Ａｒ和Ａｒ＋１０％Ｏ＿２）和不同基片偏压（－３０Ｖ到－１８０Ｖ，间隔－３０Ｖ）下，由烧结Ａｌ＿２Ｏ＿３靶材制备Ａｌ＿２Ｏ＿３薄膜。测试了样品的介电强度和沉积速率，对部分样品的结构和成份分别用ＸＰＳ和Ｘ射线进行了分析。结果表明：薄膜均呈非晶态；在两种工作气体中，随着基片负偏压的升高，沉积速率和介电强度均下降，但在－６０Ｖ偏压时，介电强度具有最大值。含氧的工作气体导致沉积速率下降，但提高了介电强度。在含氧和－６０Ｖ偏压下，Ａｌ＿２Ｏ＿３薄膜的平均介电强度为３．４６ＭＶ／ｃｍ。纯氩气氛中制备的Ａｌ＿２Ｏ＿３薄膜是缺氧的，而含氧的工作气体可使薄膜中的氧含量提高。     

Ga2O3缓冲层厚度对柔性衬底沉积Cu/ITO薄膜性能的影响

Cu and Cu/ITO films were prepared on polyethylene terephthalate （PET） substrates with a Ga2O3 buffer layer using radio frequency （RF） and direct current （DC） magnetron sputtering. The effect of Cu layer thickness on the optical and electrical properties of the Cu film deposited on a PET substrate with a Ga2O3 buffer layer was studied, and an appropriate Cu layer thickness of 4.2 nm was obtained. Changes in the optoelectrical properties of Cu（4.2 nm）/ITO（30 nm） films were investigated with respect to the Ga2O3 buffer layer thickness. The optical and electrical properties of the Cu/ITO films were significantly influenced by the thickness of the Ga2O3 buffer layer. A maximum transmission of 86%, sheet resistance of 45 Ω/□ and figure of merit of 3.96 × 10^-3 Ω^ -1 were achieved for Cu（4.2 nm）/ITO（30 nm） films with a Ga2O3 layer thickness of 15 nm.     

背表面形貌对硅太阳电池效率的影响

Different processes are used on the back surface of silicon wafers to form cells falling into three groups：textured, planar, and sawed-off pyramid back surface.The characteristic parameters of the cells, ISC, VOC, FF, Pm, and Eff, are measured.All these parameters of the planar back surface cells are the best.The FF, Pm, and Eff of sawed-off pyramid back surface cells are superior to textured back surface cells, although ISC and VOC are lower.The parasitic resistance is analyzed to explain the higher FF of the sawed-off pyramid back surface cells.The cross-section scanning electron microscopy（SEM） pictures show the uniformity of the aluminum-silicon alloy, which has an important effect on the back surface recombination velocity and the ohmic contact.The measured value of the aluminum back surface field thickness in the SEM picture is in good agreement with the theoretical value deduced from the Al-Si phase diagram.It is shown in an external quantum efficiency（EQE） diagram that the planar back surface has the best response to a wavelength between 440 and 1000 nm and the sawed-off back surface has a better long wavelength response.     

PECVD沉积双层SiNx对太阳电池性能的影响

提出了一种简单有效的制备双层SiNx薄膜的方法,其薄膜具有良好的减反射钝化特性。采用等离子体增强化学气相沉积(PECVD)的方法,通过控制SiH4和NH3气体流量比,在p型多晶硅衬底上生长单层及双层SiNx膜。随后使用薄膜测试分析仪测量了薄膜的厚度、折射率及反射率,并用Semilab WT-2000测量少数载流子寿命,通过测量量子效率,对单、双层膜电池进行了比较。实验结果表明:相比单层减反射钝化膜,采用双层SiNx膜,少数载流子寿命可以得到更好的改善,开路电压可提高约2 mV,短路电流可提高约40 mA,电池效率能提高0.15%。     

硅系太阳电池表面钝化技术比较

通过对硅片的少数载流子有效寿命、硅太阳电池的反射损失和光谱响应这三个方面的研究,比较了目前主要的硅太阳电池表面钝化技术,对这些钝化技术的优缺点进行了分析和评价.从上述三个方面的比较可以看出,RTO/SiNx堆叠钝化技术在提高硅太阳电池性能上是最优的,具有良好的应用前景.     

电子束辐照下的石墨烯上的原子层沉积Al2O3介质层

为了研究石墨烯与高k介质的结合,使用原子层沉积氧化铝在石墨衬底上。沉积前使用电子束辐照,观测到了氧化铝明显改善的形貌。归因于电子束辐照过程中的石墨层的无定形变化过程。     

热原子层沉积技术制备TiAlCN薄膜的特性

在Si和SiO2基底上,采用热原子层沉积技术,以四(二甲基氨基)钛(Ti(N (CH3)2)4)和三甲基铝(Al (CH3)3)为前驱体,制备TiAlCN薄膜.测试结果表明,随着基底温度的升高,膜层的沉积速率升高,电阻率降低,光学带隙由3.45 eV降低到2.00 eV,并在基底温度为300和350℃时出现了双吸收边;基底温度为350℃时,Al (CH3)3分解,使Al进入膜层与TiN和TiC形成TiAlN和TiAlC;膜层中TiN和TiC的形成,可以有效抑制膜层的自然氧化;基底温度为250和300℃时,薄膜为无定型结构,当基底温度为350℃时,有TiN晶体产生;膜层的表面粗糙度随着基底温度的升高先降低后升高,表面粗糙度的升高可能是因为在基底温度为350℃时前驱体材料的分解,使C-H键进入膜层所导致的.     

Excellent performance of gas sensor based on In2O3-Fe2O3 nanotubes

In₂O₃-Fe₂O₃ nanotubes are synthesized by an electrospinning method. The as-synthesized materials are characterized by scanning electron microscope and X-ray powder diffraction. The gas sensing results show that In₂O₃-Fe₂O₃ nanotubes exhibit excellent sensing properties to acetone and formaldehyde at different operating temperatures. The responses of gas sensors based on In₂O₃-Fe₂O₃ nanotubes to 100 ppm acetone and 100 ppm formaldehyde are 25 (240℃) and 15 (260℃), and the response/recovery times are 3/7 s and 4/7 s, respectively. The responses of In₂O₃-Fe₂O₃ nanotubes to 1 ppm acetone (240℃) and formaldehyde (260℃) are 3.5 and 1.8, respectively. Moreover, the gas sensor based on In₂O₃-Fe₂O₃ nanotubes also possesses an excellent selectivity to acetone and formaldehyde.     

Effects of surface passivation during atomic layer deposition of Al2O3 on In0.53Ga0.47As substrates

In this work we investigate the effect of different III-V surface passivation strategies during atomic layer deposition of Al₂O₃. X-ray photoelectron spectroscopy indicates that bare As-decapped and sulfur passivated In_0.53Ga_0.47As present residual oxides on the surface just before the beginning of the Al₂O₃ deposition while the insertion of a Ge interface passivation layer results in an almost oxide free Ge/III-V interface. The study of the initial growth regimes, by means of in situ spectroscopic ellipsometry, shows that the growth of Al₂O₃ on Ge leads to an enhanced initial growth accompanied by the formation of Ge-O-Al species thus affecting the final electrical properties of the stack. Alternatively, deposition on decapped and S-passivated In_0.53Ga_0.47As results in a more controlled growth process. The sulfur passivation leads to a better electrical response of the capacitor that can be associated to a lower oxide/semiconductor interface trap density.     

Atomic-layer-deposited Al2O3 and HfO2 on GaN: A comparative study on interfaces and electrical characteristics

Al₂O₃, HfO₂, and composite HfO₂/Al₂O₃ films were deposited on n-type GaN using atomic layer deposition (ALD). The interfacial layer of GaON and HfON was observed between HfO₂ and GaN, whereas the absence of an interfacial layer at Al₂O₃/GaN was confirmed using X-ray photoelectron spectroscopy and transmission electron microscopy. The dielectric constants of Al₂O₃, HfO₂, and composite HfO₂/Al₂O₃ calculated from the C-V measurement are 9, 16.5, and 13.8, respectively. The Al₂O₃ employed as a template in the composite structure has suppressed the interfacial layer formation during the subsequent ALD-HfO₂ and effectively reduced the gate leakage current. While the dielectric constant of the composite HfO₂/Al₂O₃ film is lower than that of HfO₂, the composite structure provides sharp oxide/GaN interface without interfacial layer, leading to better electrical properties.     

CaF2 surface passivation of lead selenide grown on BaF2

A new method of surface passivation of PbSe epitaxial layers by growing a thin epitaxial CaF₂ layer is proposed. Improvement in photoluminescence (PL) intensity is observed when the PbSe layer is passivated. The minority carrier lifetime (τ), measured by photo-current decay method corroborates PL measurements and shows a consistent, albeit not considerable, improvement in the lifetime of PbSe samples after surface passivation. The positive effect of surface passivation, especially at low heat-sink temperature, offered by a new passivating material is critically important for IV-VI material-based infrared detector and sensor applications.     

Resistive switching characteristics of Sm2O3 thin films for nonvolatile memory applications

This study investigates a sputtered Sm₂O₃ thin film to apply into a resistive random access memory device. The proposed device exhibits a stable resistance ratio of about 2.5 orders after 10⁴ cycling bias pulses and no degradation for retention characteristics monitored after an endurance test at 85 °C. The conduction mechanisms for low and high resistance states are dominated by ohmic behavior and trap-controlled space-charge limited current, respectively. The resistance switching is ascribed to the formation/rupture of conductive filaments.     

采用ALD Al2O3作为栅介质的薄势垒增强型AlGaN/GaN MIS-HEMT

本文报道了高性能的增强型（E-mode）氮化镓（GaN）基金属-绝缘体-半导体高电子迁移率晶体管（MIS-HEMT）,该器件势垒层为5-nm厚的铝镓氮（Al0.3Ga0.7N）,并采用氮化硅（SiN）钝化来控制二维电子气（2DEG）密度。与SiN钝化不同,采用原子层淀积（ALD）技术生长的氧化铝（Al2O3）不会增强异质结中的2DEG密度。刻蚀栅区的SiN介质可以耗尽沟道电子,之后采用ALD Al2O3作为栅介质,可以实现MIS结构。栅长为1 μm的E-mode MIS-HEMT具有657mA/mm的最大饱和电流（IDS）、187mS/mm的最大跨导（gm）和1V的阈值电压（Vth）。与相应的E-mode HEMT对比,由于Al2O3栅介质的引入,使器件的性能得到了很大的提升。本文对于同时实现高的Vth和IDS提供了很好的方法。     

Co3O4/Fe2O3异质结复合材料的制备及其紫外光光电探测性能

分别采用旋涂法和水热法在FTO衬底上制备Co₃O₄种子层和Co₃O₄薄膜,再在Co₃O₄薄膜上水热生长Fe₂O₃纳米棒,获得了高质量的Co₃O₄/Fe₂O₃异质结复合材料。通过改变Fe₂O₃前驱体溶液浓度来改变异质结复合材料中Fe₂O₃组分的含量。结果表明,Fe₂O₃纳米棒覆盖在呈网状结构的Co₃O₄薄膜上,随着Fe₂O₃前驱体溶液浓度即Fe₂O₃组分含量的增加,Co₃O₄/Fe₂O₃异质结复合材料对紫外光的响应逐渐增强,当Fe₂O₃前驱体溶液浓度为0.015mol/L时,异质结复合材料有着很好的光电稳定性,并表现出较高的响应率(12.5mA/W)和探测率(4.4×10¹⁰Jones)。     

Nanostructure effect of V2O5 buffer layer on performance of polymer-fullerene devices

Nanostructure of solar cell materials is often essential for the device performance. V₂O₅ nanobelt structure is synthesized with a solution process and further used as an anode buffer layer in polymer solar cells, resulting insignificantly improved power conversion efficiency (PCE of 2.71%) much higher than that of devices without the buffer layer (PCE of 0.14%) or with V₂O₅ powder as the buffer layer (1.08%). X-ray diffraction (XRD) results indicate that the V₂O₅ nanobelt structure has better phase separation while providing higher surface area for the P3HT:PCBM active layer to enhance photocurrent. The measured impedance spectrums show that the V₂O₅ nanobelt structure has faster charge transport than the powder material. This work clearly demonstrates that V₂O₅ nanobelt has great potential as a substitute of the conventionally used PEDOT-PSS buffer layer for high performance devices.