400cm2 a-Si/a-Si叠层太阳电池的研究

以全部国产化装备和工业用原材料，以简单铝背电极制备出初始效率为８．２８％，经室外阳光照射一年后稳定效率为７．３５％，面积为２０ｃｍ×２０ｃｍ，有效面积为３６０ｃｍ２ａ－Ｓｉ／ａ－Ｓｉ叠层太阳电池。主要制备技术措施：（１）ＴＣＯ／ｐ界面接触特性的改善；（２）μｃ－ＳｉＣ∶Ｈ／ａ－ＳｉＣ∶Ｈ复合窗口层技术；（３）ｐ／ｉ界面Ｈ处理；（４）高质量本征ａ－Ｓｉ∶Ｈ材料；（５）优良的ｎ１／ｐ２隧道结；（６）最佳电池结构设计等。     

大面积集成型a－SiC：H／a－Si：H叠层太阳电池的研制

报道了大面积（２７９０ｃｍ２）集成型ａ－ＳｉＣ：Ｈ／ａ－Ｓｉ：Ｈ叠层太阳电池的研制及稳定性实验结果，讨论了限制该电池效率的一些因素。实验电池的性能参数：Ｖｏｃ＝４０．８Ｖ，ＩＳＣ＝５３０．４０ｍＡ，ＦＦ＝４９．４％，有效面积（２２８０ｃｍ２）光电转换效率ＥＦ＝４．６９％（ＡＭ１．５，１００ｍＷｃｍ－２，２５℃）。制备出光电子学性能优良的ａ－ＳｉＣ：Ｈ薄膜及解决电池内部ｎ／Ｐ结的接触问题是提高该电池性能的关键。     

p／i界面的缓变层对大面积（2790cm^2）a—Si：H太阳电池性能影响的研究

报道了在大面积（２７９０ｃｍ２）ｐ－ｉ－ｎ型ａ－Ｓｉ∶Ｈ异质结太阳电池ｐ／ｉ界面之间引入缓变层（ＣＧＬ∶Ｃ，ＣＧＬ∶Ｂ∶Ｃ）对电池性能影响的研究结果。实验发现，带有ＣＧＬ∶Ｃ的ａ－Ｓｉ∶Ｈ太阳电池性能的改善主要来源于开路电压的提高，带有ＣＧＬ∶Ｂ∶Ｃ的ａ－Ｓｉ∶Ｈ太阳电池性能的提高主要来源于填充因子ＦＦ的增加。提出了带有缓变层ａ－Ｓｉ∶Ｈ电池的能带模型，据此分析了ｐ／ｉ结附近载流子的复合动力学过程，从理论上解释了实验中所发现的现象。     

SnO_2／p接触特性对a－Si太阳电池填充因子的影响

用ＰＥＣＶＤ方法制备出高电导率（～０．２ｓｃｍ－１）、宽带隙（～２．２ｅＶ）的Ｐ型微晶化硅碳合金（ｐ－μｃ－ＳｉＣ：Ｈ）薄膜材料。利用ｐ－μＣ－ＳｉＣ：Ｈ／ｐ－ａ－Ｓｉ：Ｈ复合结构做ａ－Ｓｉ太阳电池的窗口材料，明显改善了ＳｎＯ２／ｐ之间的接触特性，从而使１０ｃｍ×１０ｃｍ单结集成型电池的填充因子从０．７０以下提高到０．７２。     

AlxGa1—xAs／GaAs太阳电池减反射膜的研究

以太阳电池的短路电流积分表达式为依据，应用减反射膜的光学原理，对具有阳极氧化、ＳｉＯ和ＳｉＯ２三种减反射膜的ＡｌｘＧａ１－２Ａｓ／ＧａＡｓ太阳电池分别进行了反射光谱、短路电流、开路电压的实验测试。研究表明，阳极氧化膜、ＳｉＯ膜具有良好的减反射性能，而ＳｉＯ２膜的减反射性能较差。     

带有缓变层的大面积集成型a—Si：H太阳电池的研制

报道了把缓变层用于大面积（２７９０ｃｍ＾２）单结集成型ａ－Ｓｉ：Ｈ太阳电池板工业化生产的研究工作。分析了它对太阳电池板性能参数Ｖｏｃ，Ｉｓｃ、ＦＦ、η的影响和对提高ａ－Ｓｉ：Ｈ太阳电池板转换效率的作用。试验所得电池板的平均开路电压达２５．１Ｖ，平均转换效率达６．２％，分别比同时生产的无缓变层电池板的水平提高９．１３％和１６．９８％。试验中最好的电池板开路电压达２５．６Ｖ，转换效率达６．６％。     

带有缓变层的大面积集成型a－Si：H太阳电池的研制

报道了把缓变层用于大面积（２７９０ｃｍ２）单结集成型ａ－Ｓｉ：Ｈ太阳电池板工业化生产的研究工作。分析了它对太阳电池板性能参数Ｖｏｃ、Ｉｓｃ、ＦＦ、η的影响和对提高ａ－Ｓｉ：Ｈ太阳电池板转换效率的作用。试验所得电池板的平均开路电压达２５．１Ｖ，平均转换效率达６．２％，分别比同时生产的无级变层电池板的水平提高９．１３％和１６．９８％。试验中最好的电池板开路电压达２５．６Ｖ，转换效率达６．６％。     

高效非晶硅叠层太阳电池的优化设计

研究了高效ａ－Ｓｉ／ａ－Ｓｉ／ａ－Ｓｉ－ＳｉＧｅ三结太阳电池的优化设计。电流匹配是影响二端子叠层太阳电池填充因子的关键因素，在内电极的ｐ／ｎ界面外附加载流子复合是由少数载流子浓度、界面态和ｐ／ｎ界面处材料的几何因素匹配决定的。利用适当的带隙匹配和ｉ层厚度匹配来实现ａ－Ｓｉ／ａ－Ｓｉ／ａ－ＳｉＧｅ三结太阳电池结构的最佳化，同时采用改善ｎ／ｉ界面特性的缓冲层技术，获得了Ｖｏｃ＝２．４８Ｖ，Ｊｓｃ＝６．     

a—Si：H薄膜的表面缺陷研究

ａ－Ｓｉ：Ｈ薄膜的缺陷会给以该材料制作的半导体器件，如太阳电池、激光唱盘、光导鼓足干劲、ＴＦＴ等造成疵点，降低器件的质量和成品率；而对微波功率器件，这些缺陷则是致命的危害。本文讨论表面上由细微颗粒造成的各种缺陷，提示这些缺陷的微结构形貌，对其形成的原因进行理论分析，并就如何消除这些缺陷，制备光洁哪镜的ａ－Ｓｉ：Ｈ薄膜进行讨论。     

a－Si：H薄膜的表面缺陷研究

ａ－Ｓｉ：Ｈ薄膜的缺陷会给以该材料制作的半导体器件，如太阳电池、激光唱盘、光导鼓、ＴＦＴ等造成疵点，降低器件的质量和成品率；而对微波功率器件，这些缺陷则是致命的危害。本文讨论表面上由细微颗粒造成的各种缺陷。揭示这些缺陷的微结构形貌，对其形成的原因进行理论分析，并就如何消除这些缺陷，制备光洁如镜的ａ－Ｓｉ：Ｈ薄膜进行讨论。     

Flexible amorphous and microcrystalline silicon tandem solar modules in the temporary superstrate concept

Encapsulated and series-connected amorphous silicon (a-Si:H) and microcrystalline silicon (μc-Si:H) based thin film silicon solar modules were developed in the superstrate configuration using an aluminum foil as temporary substrate during processing and a commodity polymer as permanent substrate in the finished module. For the development of μc-Si:H single junction modules, aspects regarding TCO conductivity, TCO reduction, deposition uniformity, substrate temperature stability and surface morphology were addressed. It was established that on sharp TCO morphologies where single junction μc-Si:H solar cells fail, tandem structures consisting of an a-Si:H top cell and a μc-Si:H bottom cell can still show a good performance. Initial aperture area efficiencies of 8.2%, 3.9% and 9.4% were obtained for fully encapsulated amorphous silicon (a-Si:H) single junction, microcrystalline silicon (μc-Si:H) single junction and a-Si:H/μc-Si:H tandem junction modules, respectively.     

The influence of operation temperature on the output properties of amorphous silicon-related solar cells

The influence of the operation temperature on the output properties of solar cells with hydrogenated amorphous silicon (a-Si:H) and hydrogenated amorphous silicon germanium (a-SiGe:H) photovoltaic layers was investigated. The output power after longtime operation of an a-Si:H single junction, an a-Si:H/a-Si:H tandem, and an a-Si:H/a-SiGe:H tandem solar cell was calculated based on the experimental results of two types of temperature dependence for both conversion efficiency and light-induced degradation. It was found that the a-Si:H/a-SiGe:H tandem solar cell maintained a higher output power than the others even after longtime operation during which a temperature range of 25°C to 80°C. These results confirm the advantages of the a-Si:H/a-SiGe:H tandem solar cell for practical use, especially in high-temperature regions.     

Impact of environment factors on solar cell parameters of a-Si∥μc-Si photovoltaic modules

The behavior of amorphous silicon∥micro crystalline silicon (a-Si∥μc-Si) tandem-type photovoltaic (PV) module is complex because the output current is limited by the lower current component cell. Also, the outdoor behaviors are not fully understood. The impact of environment factors on solar cell parameters of a-Si∥μc-Si PV module was quantitatively analyzed and the module was compared with other silicon-based PV modules (single crystalline silicon (sc-Si) and amorphous silicon (a-Si)). The contour maps of solar cell parameters were constructed as a function of irradiance and module temperature. The contour map of a-Si∥μc-Si PV modules is similar to that of a-Si modules. The results imply that output characteristics of a-Si∥μc-Si PV modules are mainly influenced by the a-Si top cell. Furthermore, the efficiency of a-Si∥μc-Si PV modules was compared other solar cell parameters and the contour map of efficiency is similar to that of fill factor.     

Fabrication technology for large-area a-Si solar cells

The fabrication process technology for large-area a-Si photovoltaic (PV) modules and their performance are reviewed. Our present technology enables us to provide 10% efficient large-area submodules with a stabilized efficiency of 8.5%. To study the practicability of the a-Si solar panels, we carried out an outdoor test for our a-Si modules. The results show that the a-Si solar PV modules generate power very efficiently in outdoor systems. The advantage of the a-Si modules under outdoor uses is presented and discussed.     

Spectral effects on amorphous silicon solar module fill factors

The outdoor operation and monitoring of amorphous silicon (a-Si) solar modules present unique features when compared to the more traditional and quite well understood operation of the crystalline silicon (c-Si) technology. The peculiarities of a-Si contrast to such extent with those of c-Si solar cells that in the field, while the former performs better during summer, the latter is more efficient in winter. Concepts usually applied to describe phenomena in c-Si devices are often inadequate to describe the performance of a-Si cells. When looking at module performance, the fill factor (FF) can be regarded as one of the characteristic photovoltaic quantities of major interest. Under outdoor illumination, cells are seasonally exposed to different solar spectral contents and intensities, which vary considerably from summer to winter. The FF depends on both the quality (spectrum) and quantity (irradiation) of the incident light. In this context, we report results showing spectral effects on the FF of amorphous silicon solar modules deployed outdoors. While “blue” spectra improved the FF of a-Si devices, the contrary was observed for “red” spectra. The voltage-dependent spectral response of a-Si devices is also described and quantified. Our results reveal that a-Si modules can perform quite well at low irradiations and mainly diffuse spectra. We, thus, conclude that in system sizing programmes, the performance of a-Si modules should be treated more precisely with respect to spectra, to reveal their true operational characteristics and advantages.     

Seasonal variations in amorphous silicon solar module outputs and thin film characteristics

Hydrogenated amorphous silicon (a-Si:H) solar modules exposed to outdoor conditions exhibit, over a long-time scale, an efficiency pattern which improves during summer months and decreases in winter time. The variations are usually attributed to two main mechanisms: (a) thermal annealing effects enhanced by summer month temperatures, which might partly offset the efficiency decrease caused by light-induced changes in the amorphous silicon material (known as the Staebler-Wronski effect), and (b) seasonal spectral variations in the solar radiation reaching the earth's surface, which are quite marked in the wavelength region in which amorphous silicon solar cells respond. While both factors might contribute to a more severe performance degradation in winter, we show, by exposing both commercial a-Si : H solar modules and thin films to the same AM 1.0 spectrum while keeping them at temperatures corresponding to extreme summer and winter operating cell temperatures, that the second effect might be the major factor in the overall seasonal efficiency changes. Light-induced annealing, enhanced by the higher radiation levels to which modules are exposed during summer months, might be playing a role as well, adding extra complexity to the effect.     

Optical modelling of a single-junction p-i-n type and tandem structure amorphous silicon solar cells with perfect current matching

Using the admittance analysis method, the optimal design of a single junction a-Si : H solar cell is suggested and its photovoltaic parameters are calculated. The technique is then extended to design a tandem structure of two cells stacked one on the top of the other and connected in series. The top cell is considered of a-Si : H and bottom of a-SiGe : H and the condition of current matching is applied to determine the tandem's optimal design. The efficiency of the single-junction cell with the optimal design is predicted to be 13.1% and that of the tandem cell with the perfect current matching is 20.8%. The results of our calculations are discussed in the light of the recent experimental results.     

Surface textured MF-sputtered ZnO films for microcrystalline silicon-based thin-film solar cells

Highly conductive and transparent aluminum-doped zinc oxide (ZnO:Al) films were prepared by reactive mid-frequency (MF) magnetron sputtering at high growth rates. By varying the deposition pressure, pronounced differences with respect to film structure and wet chemical etching behavior were obtained. Optimized films develop good light-scattering properties upon etching leading to high efficiencies when applied to amorphous (a-Si:H) and microcrystalline (μc-Si:H) silicon-based thin-film solar cells and modules. Initial efficiencies of 7.5% for a μc-Si:H single junction and 9.7% for an a-Si:H/μc-Si:H tandem module were achieved on an aperture area of 64 cm².     

Field and laboratory studies of the stability of amorphous silicon solar cells and modules

If photovoltaic solar cells and modules are to be used as a major source of power generation it is important to have a good knowledge and understanding of their long-term performance under different climatic and operating conditions. A number of studies of the long-term performance of commercially available photovoltaic modules manufactured using different technologies have now been reported in the literature. These have shown clear differences in the seasonal and long term performance and stability of different solar cell techniques. In addition to general module engineering factors that result in a loss of performance in all modules some types of solar cells, such as those made from thin film amorphous silicon (a-Si:H), also suffer specific losses in performance due to fundamental material changes, such as photodegradation or the Staebler–Wronski effect (SWE). A field evaluation of the long term performance of state-of-the-art crystalline and amorphous silicon photovoltaic modules in Australian conditions is currently being undertaken at Murdoch University. The initial results from this monitoring program are reported. This paper also reports on laboratory and field studies being undertaken on the nature of the Staebler–Wronski effect in amorphous silicon solar cells and how the stability of these cells is affected by different operating conditions. Based on a mechanism for the SWE in a-Si:H solar cells developed as a result of our research we propose a number of possible ways to reduce the Staebler–Wronski effect in a-Si:H solar cells.     

Outdoor exposure tests of photovoltaic modules in Japan and overseas

In order to evaluate the reliability and performances of photovoltaic (PV) modules, it is of importance to reveal the characteristics of PV modules in actual use conditions. Outdoor exposure tests of PV modules have been conducted at some sites in Japan and Australia. The purpose of these tests are to evaluate the effects of the starting month of exposure, long term degradation, and heat insulator on the performances of the module efficiencies. Some important results were obtained, for example, the efficiencies of a-Si modules after one year of exposure showed similar tendencies regardless of the starting month of the year. The efficiencies of a-Si modules showed no long term (for six years) degradation. Heat insulator had the effects on the increase of the module temperature and the corrected (by irradiance and temperature) output power. For the outdoor exposure tests with much more severe conditions, the climate conditions of Oman were examined and found to be a suitable place due to its high solar irradiance, temperature, and humidity.