氮化硅薄膜对晶体硅材料和电池的钝化效果研究

利用等离子体增强化学气相沉积技术,在P型直拉单晶硅硅片和铸造多晶硅片以及太阳电池的表面上 沉积了非晶氮化硅(a-SiNx:H)薄膜,并研究了氮化硅薄膜对材料少子寿命和太阳电池性能的影响。研究发现: 氮化硅薄膜显著地提高了晶体硅材料中少子寿命,同时多晶硅太阳电池的开路电压有少量提高,短路电流普遍 提高了1mA/cm2,电池效率提高了2％。实验结果表明:氮化硅薄膜不仅具有表面钝化作用,也有良好的体钝化 作用。     

氮化硅薄膜对硅片背表面的钝化作用

采用等离子体增强化学沉积的方法(PECVD),在低衬体温度下制备不同厚度的双面氮化硅薄膜,通过准稳态电导法(QSSPCD)测试non-diffused和diffused硅片沉积不同厚度双面氮化硅薄膜烧结前后的少子寿命,研究发现,氮化硅薄膜厚度在17 nm左右的时候,背面钝化效果有所下降,超过26 nm的时候,效果基本一致.non-diffused烧结后的少子寿命下降很大,而diffused与之相反.结果表明,采用氮化硅作为背面钝化介质膜,可以改善材料的少子寿命,背面钝化膜可以选择在26～75 nm之间.     

热处理对氮化硅薄膜光学和电学性能的影响

使用PECVD在单晶硅硅片表面沉积了非晶氮化硅(a-SiNx∶H)薄膜,采用传统的退火炉和快速热退火炉进行了不同时间和温度下的退火比较,并研究了退火对薄膜光学性能以及材料少子寿命的影响。研究发现:氮化硅薄膜经热处理后厚度降低,折射率先升高后降低;沉积氮化硅薄膜后400℃退火可以促进氢扩散,提高少子寿命,超过400℃后氢开始逸失,衬底少子寿命急剧下降。另外,还发现RTP处理过程中氢的逸失比常规热处理快。     

多晶硅太阳电池预处理及退火工艺研究

在沉积氮化硅薄膜之前采用氨气电离出氢等离子体,先对硅片进行氢等离子体预处理,通过数值分析和实验方法分别研究预处理时间、功率、温度、压力等各参数对钝化效果以及电学性能的影响。在预处理温度450℃,时间200s,射频功率4000W,气体压强200Pa,氨气流量4000sccm/min时,短路电流提高约4%。采用等离子体增强型的化学气相沉积(PECVD)法,在电池表面镀上一层氮化硅膜,实验证实氢等离子体会透过氮化硅进入到硅基体内,从而使少子寿命提高约5μs。低温退火实验表明,430~440℃为最优温度,随时间的增加,短路电流有明显提升。     

PECVD制备太阳电池氮化硅薄膜特性研究

含氢氮化硅薄膜在太阳电池工业生产领域被广泛的用作减反射层和钝化层。使用工业型等离子体增强化学气相沉积(PECVD)设备制备了含氢氮化硅薄膜,使用傅里叶红外光谱(FTIR)测试仪对薄膜成分进行分析,研究反应气体流量、高频电源功率对薄膜成分以及薄膜特性影响,并通过硅片的少子寿命研究氮化硅薄膜成分对硅片钝化效果的影响,明确实际工业生产中的工艺调整方向。     

多晶硅太阳电池少子寿命的数值模拟

主要引入载流子的有效迁移率和有效扩散长度两个物理量,对多晶硅的少子寿命进行数值模拟.在此基础上建立了多晶硅太阳电池的一维物理模型,采用数值模拟方法对其在AM1.5太阳光入射下的电池输出特性Lsc、Voc、FF和η进行模拟计算,着重分析了晶粒尺寸和基区少子寿命对多晶硅太阳电池性能的影响.模拟结果表明,晶粒尺寸和少子寿命是影响多晶硅太阳电池性能的两个关键因素.当少子寿命较低时,晶粒尺寸对电池效率的影响不大,此时电池效率的提高受限于少子寿命;当少子寿命增大时,电池效率随晶粒尺寸的增大显著提高.同时,从模拟结果可得到电池效率与少子寿命和晶粒尺寸之间的定量关系.     

氮化硅薄膜的性能研究以及在多晶硅太阳电池上的应用

利用椭圆偏振仪、准稳态光电导衰减法(QSSPCD)、X射线光电子能谱(XPS)、红外吸收光谱(IR)、反射谱等手段，研究了不同硅烷和氨气配比条件以及沉积温度对在多晶硅太阳电池上所沉积的氮化硅薄膜性能的影响，优化了沉积条件。通过比较沉积前后电池的各项性能，确认经氮化硅钝化后电池效率提高了40％以上，电池的短路电流也提高了30％以上，对于电池的开路电压提高也很大.     

少子寿命值对太阳电池生产的监控作用

研究了太阳电池工艺过程中少子寿命值的变化,揭示了少子寿命值在太阳电池生产过程中的应用.通过比较工艺前后少子寿命值的变化,可以优化生产工艺,提高电池转换效率,改善电池的性能.经过工艺优化后,多晶硅太阳电池(非绒面)的平均转换效率达到14.75%.     

玻璃衬底多晶硅薄膜太阳电池的制备

多晶硅薄膜太阳电池兼具单晶硅的高转换效率和多晶硅体电池的长寿命的特点,其制备工艺比非晶硅薄膜材料的制备工艺相对简化。文章介绍了多晶硅薄膜太阳电池材料制备工艺和材料性能;阐述了多晶硅薄膜太阳电池Si3N4膜的沉积和玻璃制绒等关键工艺;综述了玻璃衬底多晶硅薄膜太阳电池的发展现状。     

表面处理与p层电导率对HIT电池性能的影响

考虑到氢氟酸溶液对晶体硅表面具有去氧化和氢离子钝化表面悬键的双重作用,通过优化清洗工艺使得a-Si∶H(i)/c-Si/a-Si∶H(i)异质结构有效少子寿命达到2 ms。研究不同沉积温度对p型非晶硅薄膜电导率的影响,结合后退火发现中温(150℃)生长高温后退火的方式优于直接高温(200℃)沉积,电导率和钝化效果都有明显改善。采用优化后的p层,a-Si∶H(p~+)/a-Si∶H(i)/c-Si/a-Si∶H(i)/a-Si∶H(n~+)(inip)结构少子寿命可达3.70 ms。制备的HIT电池具有优良的性能:开路电压V_(oc)=700 mV,潜在的填充因子pFF=82%,短路电流密度Jsc=32.10 mA/m~2,填充因子FF=72.35%,转换效率η=16.26%,对比Suns-V_(oc)I-V曲线和标准条件下测试的I-V曲线计算得串联电阻,分析FF与pFF差异的原因。     

New materials and deposition techniques for highly efficient silicon thin film solar cells

This paper reviews recent efforts to provide the scientific and technological basis for cost-effective and highly efficient thin film solar modules based on amorphous (a-Si:H) and microcrystalline (μc-Si:H) silicon. Textured ZnO:Al films prepared by sputtering and wet chemical etching were applied to design optimised light-trapping schemes. Necessary prerequisite was the detailed knowledge of the relationship between film growth, structural properties and surface morphology obtained after etching. High rate deposition using plasma enhanced chemical vapour deposition at 13.56 MHz plasma excitation frequency was developed for μc-Si:H solar cells yielding efficiencies of 8.1% and 7.5% at deposition rates of 5 and 9 Å/s, respectively. These μc-Si:H solar cells were successfully up-scaled to a substrate area of 30×30 cm² and applied in a-Si:H/μc-Si:H tandem cells showing initial test cell efficiencies up to 11.9%.     

Novel device structure for Cu(In,Ga)Se2 thin film solar cells using transparent conducting oxide back and front contacts

Cu(In_1−xGa_x)Se₂ (CIGS)-based thin film solar cells fabricated using transparent conducting oxide (TCO) front and back contacts were investigated. The cell performance of substrate-type CIGS devices using TCO back contacts was almost the same as that of conventional CIGS solar cells with metallic Mo back contacts when the CIGS deposition temperatures were below 500 °C for SnO₂:F and 520 °C for ITO. CIGS thin film solar cells fabricated with ITO back contacts had an efficiency of 15.2% without anti-reflection coatings. However, the cell performance deteriorated at deposition temperatures above 520 °C. This is attributed to the increased resistivity of the TCO’s due to the removal of fluorine from SnO₂ or undesirable formation of a Ga₂O₃ thin layer at the CIGS/ITO interface. The formation of Ga₂O₃ was eliminated by inserting an intermediate layer such as Mo between ITO and CIGS. Furthermore, bifacial CIGS thin film solar cells were demonstrated as being one of the applications of semi-transparent CIGS devices. The cell performance of bifacial devices was improved by controlling the thickness of the CIGS absorber layer. Superstrate-type CIGS thin film solar cells with an efficiency of 12.8% were fabricated using a ZnO:Al front contact. Key techniques include the use of a graded band gap Cu(In,Ga)₃Se₅ phase absorber layer and a ZnO buffer layer along with the inclusion of Na₂S during CIGS deposition.     

CdS/CdTe太阳电池中CdS多晶薄膜的结构和光学性能

采用XRD,AFM,XPS和光学透射谱对化学水浴法制备的CdS多晶薄膜进行了测试分析。刚沉积的CdS多晶薄膜均匀、透明、致密,主要呈现立方结构;Cd和S的原子百分比约为1 10;能隙(Eg)约为2 47eV。在不同温度下后处理会出现六方结构和3CdSO4·8H2O衍射峰,同时晶面择优取向发生了变化。通过沉积高质量的CdS薄膜,获得了效率约13 4%的CdS/CdTe小面积太阳电池。     

微晶硅材料和电池特性的相关研究

主要采用甚高频等离子体增强化学气相沉积技术制备了系列微晶硅材料和电池。通过对材料电学特性、结构特性和电池间性能关系的研究,获得了高效率微晶硅薄膜太阳电池所对应材料的基本特性:暗电导在10~(-8)s/cm量级上,光敏性大于1000,晶化率约50%。进行了制备电池的开路电压和表观带隙之间关系的研究。     

Cathodic arc deposition of solar thermal selective surfaces

There are some advantages of cathodic arc deposition techniques over other thin film deposition methods. In this paper we discuss and demonstrate the possibility of applying the cathodic arc deposition technology to the production of solar energy conversion devices, particularly solar thermal selective surfaces. We show that cathodic arc deposition can be operated in a plasma assisted chemical vapour deposition mode as well as reactive deposition mode to produce metal-dielectric cermet materials. Solar thermal selective surfaces were obtained using this method. The morphology of the surfaces can be varied from rough to smooth by controlling the macroparticles content by means of filtering. Rough but dense films can be deposited, which may have potential for enhancing solar absorption for both solar thermal selective surfaces and solar cells.     

多晶硅薄膜太阳电池的研究与进展

从薄膜的沉积方式和沉积温度以及衬底材料等几方面综合分析了多晶硅薄膜制备工艺的特点及多晶硅薄膜太阳电池的最新研究进展。并以颗粒硅带(SSP)为衬底，采用快热化学气相沉积(RTCVD)法制备了多晶硅薄膜，随后制得的多晶硅薄膜太阳电池的效率达到6．05％。     

Development of n-μc-SiOx:H as cost effective back reflector and its application to thin film amorphous silicon solar cells

Development of doped silicon oxide based microcrystalline material as a potential candidate for cost-effective and reliable back reflector layer (BRL) for single junction solar cells is discussed in this article. Phosphorus doped μc-SiO_x:H layers with a refractive index ∼2 and with suitable electrical properties were fabricated by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) technique, using the conventional capacitively coupled reactors. Optoelectronic properties of these layers were controlled by varying the oxygen content within the film. The performance of these layers as BRL have been investigated by incorporating them in a single junction amorphous silicon solar cell and compared with the conventional ZnO:Al based reflector layer. Single junction thin film a-Si solar cells with efficiency ∼9.12% have been successfully demonstrated by using doped SiO:H based material as a back reflector. It is found that the oxide based back reflector shows analogous performance to that of conventional ZnO:Al BRL layer. The main advantage with this technology is that, it can avoid the ex-situ deposition of ZnO:Al, by using doped μc-SiO:H based material grown in the same reactor and with the same process gases as used for thin-film silicon solar cells.     

Microcrystalline silicon films and solar cells deposited by PECVD and HWCVD

The application of microcrystalline silicon (μc-Si:H) in thin-film solar cells is addressed in the present paper. Results of different technologies for the preparation of μc-Si:H are presented, including plasma enhanced chemical vapour deposition (PECVD) using 13.56 MHz (radio frequency, rf) and 94.7 MHz (very high frequency, vhf) and hot-wire chemical vapour deposition (HWCVD). The influence of the silane concentration (SC) on the material and solar cell parameters is studied for the different techniques as the variation of SC allows to optimise the solar cell performance in each deposition regime. The best performance of μc-Si:H solar cells is always observed near the transition to amorphous growth. The highest efficiency obtained so far at a deposition rate of 5 Å/s is 9.4%, achieved with rf-PECVD in a deposition regime of using high pressure and high discharge power. High deposition rates and solar cell efficiencies could be also achieved by vhf-PECVD. An alternative approach represents the HWCVD which also demonstrated high deposition rates for μc-Si:H. However, good material quality and solar cell performance could only be achieved at low substrate temperatures and, consequently, low deposition rates. The μc-Si:H solar cells prepared by HWCVD exhibit comparably high efficiencies up to 9.4% and exceptionally high open circuit voltages up to 600 mV but at lower deposition rates (≈1 Å/s). The properties of PECVD and HWCVD solar cells are carefully compared.     

Electrodepostied polyaniline films decorated with nano-islands: Characterization and application as anode buffer layers in solar cells

Polyaniline (PANI) thin films studded with nano-islands on their surface are electrochemically synthesized. The surface morphology of these films can be adjusted by controlling the deposition time during the synthesis. The PANI films decorated with nano-islands are used as the buffer layer in the organic solar cells based on a blend of poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) and [6,6]-phenyl-C61 butyric acid methyl ester (PCBM). The investigation on the characteristics of the solar cells demonstrates that the nano-islands on the PANI buffer surface are helpful in improving the solar cell performance.