Dünnschichtsolarzellen

Thin Film Solar Cells The direct conversion of sunlight into electricity — photovoltaics (PV) — has emerged as a strongly growing market during the past years. Today, more than 80 % of the world market is supplied by solar modules based on mono‐ or polycrystalline silicon wafers. Thin‐film solar cells promise significantly lower costs for photovoltaic energy conversion, and thus will probably dominate the PV‐market in the future. Consequently, the production of thin film solar cells will lead to key technologies of the 21^st century. This article addresses the three most advanced types of thin‐film cells describing the status of these technologies at the laboratory level, in pilot production, and in first production lines. The challenges along the way from laboratory developments towards mass production are discussed, fo cusing on the central role of the vacuum‐based technologies applied for thin film deposition.     

Hochdurchsatzbeschichtungen für die Photovoltaik

High throughput coatings for photovoltaics – Contribution of sputtering technology to Paris Climate Goals Photovoltaics (PV) is one of the most important renewable energy sources whose expansion is needed to achieve the climate goals. The considerable drop down in the costs of PV based energy within the last 10 years has led to a very high degree of economic attractiveness for photovoltaics. This was made possible by new cell structures with higher efficiencies, lower material usage and utilization of scaling effects as well as automation in production. Highly efficient PVD coating processes, such as the magnetron sputtering, are increasingly being used in current crystalline PV cell types such as heterojunction or TOPCON solar cells. Thin film technologies are still the backbone for processing of the less material‐intensive thin‐film solar modules.     

Dünnschichtfilter in der Telekommunikation

Market forces are pushing the performance of optics to their limits. Optical components must be developed to provide the best possible combination of manufacturability, performance and price. One vital step to success in creating WDM optics lies in a discipline that is often overlooked or misunderstood – coating engineering. A key technology for controlling light in WDM systems is the optical filter, which performs functions from simple filtering in multiplexers and demultiplexers, to more sophisticated functions in optical amplifiers, modulators and test equipment. The basic tool of multiplexing and demultiplexing devices, thin film filters offer accurate center wavelength, broad flattop passband and high isolation from adjacent and nonadjacent channels. Thin film filters are widely used for gain flattening, band splitting, C and L band separation and combining amplifier‐pump beams. Choosing the right thin‐film‐deposition process is essential for the efficiency and productivity of vacuum coating systems. LEYBOLD OPTICS has developed and optimized a comprehensive range of vacuum coating processes and process tools. LEYBOLD OPTICS has been proven the ability of producing shift‐free coatings on large substrate areas by means of PIAD (Plasma Ion Assisted Deposition) in many applications over the past ten years. The low loss and stress values achieved, especially with silica and tantala films, allows besides the production of narrow band pass filters (DWDM, CWDM) also the production of gain flattening filters (GFF). PIAD is considerably improving the properties of evaporated thin films by high energy ion bombardment during the growing of the film. PIAD allows to produce dense shift free thin films with high refractive index, good adhesion and extremely low absorption. With the Advanced Plasma Source (APS) LEYBOLD OPTICS has developed a high power plasma source for PIAD. The APS provides high ion current densities over a large surface area in a neutral plasma to produce high quality layers at a high productivity.     

Manufacturing of CdTe thin film photovoltaic modules

The technology to fabricate CdTe/CdS thin film solar cells can be considered mature for a large-scale production of CdTe-based modules. Several reasons contribute to demonstrate this assertion: a stable efficiency of 16.5% has been demonstrated for 1 cm² laboratory cell and it is expected that an efficiency of 12% can be obtained for 0.6 × 1.2 m² modules; low cost soda lime float glass can be used as a substrate; the amount of source material is at least 100 times less than that used for single crystal modules and is a negligible part of the overall cost. The fabrication process can be completely automated and a production yield of one module every 2 min can be obtained, which implies a production cost substantially less than 1€/W_P. A further cost reduction will render this kind of energy production competitive with the energy obtained from fossil fuels by approaching the so-called grid-parity. Some new companies have recently announced the start of production or plan to do so in the near future. Many of these plants are located in Germany, some in the USA. In Italy, a new company has been constituted in 2008, with the aim of building a factory with a capacity of 18 MW/year. In this article, we will describe and compare the basic principles of CdTe solar cells and modules. We will include an overview of the potentials of these technologies and of the R&D issues under investigation. This paper describes how the large-area mass production of CdTe solar modules is realized in the Italian factory and presents a worldwide overview of the current production activities.     

Mikrowellen‐PECVD für kontinuierliche Großflächenbeschichtung bei Atmosphärendruck

Microwave PECVD for continuous wide area coating at atmospheric pressure Plasma processes are applied for a variety of surface modifications. Examples are coatings to achieve an improved corrosion and scratch protection, or surface cleaning. Normally, these processes are vacuum based and therefore suitable to only a limited extend for large area industrial applications. By use of atmospheric pressure plasma technology integration in continuously working manufacturing lines is advantageously combined with lower costs and higher throughput. Microwave plasma sources present powerful modules for plasma enhanced chemical vapour deposition at atmospheric pressure. At Fraunhofer IWS processes and equipment as well as application specific materials are developed. The coatings are suitable for scratch resistant surfaces, barrier and corrosion protective layers or anti‐reflex layers on solar cells. The film properties achieved are comparable with those produced by low pressure processes.     

Low‐Temperature Soft‐Cover Deposition of Uniform Large‐Scale Perovskite Films for High‐Performance Solar Cells

Large‐scale high‐quality perovskite thin films are crucial to produce high‐performance perovskite solar cells. However, for perovskite films fabricated by solvent‐rich processes, film uniformity can be prevented by convection during thermal evaporation of the solvent. Here, a scalable low‐temperature soft‐cover deposition (LT‐SCD) method is presented, where the thermal convection‐induced defects in perovskite films are eliminated through a strategy of surface tension relaxation. Compact, homogeneous, and convection‐induced‐defects‐free perovskite films are obtained on an area of 12 cm², which enables a power conversion efficiency (PCE) of 15.5% on a solar cell with an area of 5 cm². This is the highest efficiency at this large cell area. A PCE of 15.3% is also obtained on a flexible perovskite solar cell deposited on the polyethylene terephthalate substrate owing to the advantage of presented low‐temperature processing. Hence, the present LT‐SCD technology provides a new non‐spin‐coating route to the deposition of large‐area uniform perovskite films for both rigid and flexible perovskite devices.     

Ultrafast deposition of silicon nitride and semiconductor silicon thin films by hot wire chemical vapor deposition

The technology of Hot Wire Chemical Vapor Deposition (HWCVD) or Catalytic Chemical Vapor Deposition (Cat-CVD) has made great progress during the last couple of years. This review discusses examples of significant progress. Specifically, silicon nitride deposition by HWCVD (HW-SiN_x) is highlighted, as well as thin film silicon single junction and multijunction junction solar cells. The application of HW-SiN_x at a deposition rate of 3 nm/s to polycrystalline Si wafer solar cells has led to cells with 15.7% efficiency and preliminary tests of our transparent and dense material obtained at record high deposition rates of 7.3 nm/s yielded 14.9% efficiency. We also present recent progress on Hot-Wire deposited thin film solar cells. The cell efficiency reached for (nanocrystalline) nc-Si:H n-i-p solar cells on textured Ag/ZnO presently is 8.6%. Such cells, used in triple junction cells together with Hot-Wire deposited proto-Si:H and plasma-deposited SiGe:H, have reached 10.9% efficiency. Further, in our research on utilizing the HWCVD technology for roll-to-roll production of flexible thin film solar cells we recently achieved experimental laboratory scale tandem modules with HWCVD active layers with initial efficiencies of 7.4% at an aperture area of 25 cm².     

Plasmatechnik in der Photovoltaikindustrie

Application of Plasmatechnology in Photovoltaic Industry Ever since the introduction of attractive feed‐in tariffs for photovoltaic electricity generation, there has been a huge surge in all kinds of photovoltaic applications. Products based on multicrystalline wafers still have the largest market share with thin film products picking up in recent times. Manufacturers of thin film products have increased their production volume. In the meantime, production technology for wafer based solar cells has been improved. With the second generation of tools a trend towards standardization is to be noticed. Both in wafer based as well as in thin film solar cells a number of plasma processes are applied in the production process. These processes include conventional magnetron sputtering or PECVD as well as plasma chemical etch processes. In terms of thin films the portfolio ranges from the rather well known silicon nitrid or ITO films to rather more complex binary films. We will present but a few examples from the afore mentioned applications and discuss open question with respect to vacuum and machine technology.     

Rückseitenmetallisierung Wafer‐basierter Si‐Solarzellen mittels EB‐PVD

Back Side Metallization of Wafer Based Silicon Solar Cells by Means of Electron Beam Evaporation Electron beam evaporation is an innovative vacuum deposition technology regarding the wafer backside metallization of crystalline silicon solar cells. The motivation for the consideration of electron beam evaporation as cell finishing step is based on the one hand on the competition with thin film photovoltaic modules and on the other on the remarkable cost reduction potential by applying EB‐PVD (Electron Beam Physical Vapor Deposition). This article presents a highly productive coater concept and gives an explanation of important aspects for the adaption of the coater concept to typical solar cell features. Various PVD technologies are compared concerning their possible use as wafer backside metallization method. Challenges and chances of the introduction of EB‐PVD in the wafer based solar cell production are considered.     

薄膜太阳能电池的进展和展望

薄膜太阳能电池因具有价格低、弱光性好、大面积自动化生产、柔性便携等优点,表现出极大的发展意义和良好的市场前景。目前光伏市场上薄膜太阳能电池主要分为硅基薄膜太阳能电池、碲化镉薄膜太阳能电池、铜铟镓硒薄膜太阳能电池三大类。本文介绍了三种薄膜太阳能电池的发展现状,指出了它们的优点和存在的主要问题,分析了学术界和产业界针对这些问题的解决方案,展望了其发展前景。     

Pilot production of large-area CuInS2-based solar modules

A pilot production of CuInS₂-based thin-film solar modules has been established in Berlin, Germany. To date, its 125 cm × 65 cm modules have produced an aperture area conversion efficiency as high as 7.6%, and avenues towards even higher performance levels have been identified. The pilot production features industrially-proven sputtering technology for material deposition and a new rapid thermal process allowing a five-minute sulfurization cycle time. The first thousand modules produced (representing a total of 45 kWp) were subjected to statistical analysis documenting the continuous enhancement of module power over the early months of pilot production. Transient effects were found that influence module I(V) characteristics cause inaccurately low module power measurements when flasher-type sun-simulators are used in testing — a phenomenon correctable by the introduction of a pre-test light-soaking procedure. In order to verify the post-light-soaking test results data from outdoor measurements taken under standard test conditions as well as performance data of outdoor PV systems were analyzed. A higher energy output on a Wh/Wp-basis found for CuInS₂-based solar modules than for polycrystalline silicon-based solar modules is presumed to be due to a lower temperature coefficient. For evaluating the long-term future potential of the new CuInS₂-based technology, a cost model is introduced to assess the economic relevance of uptime, cycle time and yield values, and to show that both efficiency and productivity are crucial for high-capacity manufacture of thin-film solar modules.     

晶体硅薄膜电池制备技术及研究现状

晶体硅薄膜太阳电池近些年来得到广泛的研究和初步的商业化探索。根据所采用的晶体硅薄膜沉积工艺中温度范围的不同，晶体硅薄膜电池研究可分为高温路线和低温路线两个不同发展方向。本文分别从这两个方向综述了目前国外晶体硅薄膜电池制备技术的最新进展，最新实验室研究结果。报导了晶体硅薄膜电池商业化进展状况，指出了晶体硅薄膜电池实现产业化必须解决的问题。     

等离子体增强化学气相沉积设备的研制

本文介绍非晶硅薄膜太阳能电池生产线的核心设备——等离子体增强化学气相沉积(PECVD, Plasma Enhanced Chemical Vapor Deposition)系统,并阐述了其重要地位.非晶硅太阳能电池制造的关键技术是非晶硅薄膜的制备,目前最常见的制备方法是PECVD技术.PECVD技术凭借其低温沉积、可大面积成膜、成膜均匀等特点,在非晶硅薄膜制备方面迅速发展.PECVD系统用于制备非晶硅太阳能电池的关键结构P、I、N硅薄膜层.本文阐述了该设备的结构特点、技术指标、工作原理及工艺过程,对沉积室的结构和配置进行了详细设计计算,非晶硅太阳能电池稳定后的转化效率可达6％.     

UV‐Lasertechnologie in der PLD

Future of UV Lasertechnology in industrial PLD processes The success formula for any thin film technology on the production floor is bridging the gap between precisely depositing a functional thin film and at the same time achieving industrial processing rates. Fortunately, the pulsed laser deposition method has come of age thanks to output power and stability advances in UV excimer laser technology and has become a proven and industrial grade thin film deposition method.     

Interface Engineering of Inorganic Thin‐Film Solar Cells – Materials‐Science Challenges for Advanced Physical Concepts

The challenges and research needs for the interface engineering of thin‐film solar cells using inorganic‐compound semiconductors are discussed from a materials‐science point of view. It is, in principle, easily possible to define optimized device structures from physical considerations. However, to realize these structures, many materials' limitations must be overcome by complex processing strategies. In this paper, interface properties and growth morphology are discussed using CdTe solar cells as an example. The need for a better fundamental understanding of cause–effect relationships for improving thin‐film solar cells is emphasized.     

A robust and self-assembled route to synthesis of CdZn(Se<Subscript>1−x</Subscript>Te<Subscript>x</Subscript>)<Subscript>2</Subscript> photoanodes as light harvesters for photoelectrochemical solar cells

This work reports on the development of CdZn(Se_1?xTe_x)₂ thin films utilized as the photoanode for photoelectrochemical cells (PECs). It was found that the incorporation of tellurium plays an important role in determining the optostructural, morphological, compositional and PEC performance of thin films. XRD measurements showed that the deposited thin films are in the mixed phases with a nanocrystalline nature. SEM images indicated that the surface morphology is favourable for effective light absorption in the solar spectrum. The EDS spectrum confirmed that thin film deposition occured in a stoichiometric manner. A detailed quantitative study was also executed using XPS and revealed the presence of Cd²⁺, Zn²⁺, Se^2? and Te^2? elements in the deposited thin film. Finally, the deposited thin films were tested for their photoelectrochemical (PEC) performance. The PEC study illustrated that CdZn(Se_1?xTe_x)₂ thin film showed the highest power conversion efficiency (η) of 1.13% among reported values.     

Coated and Printed Perovskites for Photovoltaic Applications

Hybrid organic–inorganic metal halide perovskite semiconductors provide opportunities and challenges for the fabrication of low‐cost thin‐film photovoltaic devices. The opportunities are clear: the power conversion efficiency (PCE) of small‐area perovskite photovoltaics has surpassed many established thin‐film technologies. However, the large‐scale solution‐based deposition of perovskite layers introduces challenges. To form perovskite layers, precursor solutions are coated or printed and these must then be crystallized into the perovskite structure. The nucleation and crystal growth must be controlled during film formation and subsequent treatments in order to obtain high‐quality, pin‐hole‐free films over large areas. A great deal of understanding regarding material engineering during the perovskite film formation process has been gained through spin‐coating studies. Based on this, significant progress has been made on transferring material engineering strategies to processes capable of scale‐up, such as blade coating, spray coating, inkjet printing, screen printing, relief printing, and gravure printing. Here, an overview is provided of the strategies that led to devices deposited by these scalable techniques with PCEs as high as 21%. Finally, the opportunities to fully close the shrinking gap to record spin‐coated solar cells and to scale these efficiencies to large areas are highlighted.     

Leistungsfähige Dünnschicht‐Beschichtung für die Photovoltaik

High‐performance thin‐film coating for photovoltaic applications The thin‐film photovoltaics market is large and is expected to grow continuously. Due to its huge potential regarding cost reduction and cell efficiency improvement, sputter‐etched ZnO:Al‐based TCO can make a sustainable contribution to achieve grid parity. One of the most promising approaches here is the large scale volume manufacturing of sputter‐etched TCO glass for thin film silicon solar cells. VON ARDENNE's leading process knowhow, applied to the highly productive and reliable PIA|nova coating system, allows for cost effective production and flexible adaptation of customer specific TCO requirements.     

CdTe thin film technology: Leading thin film PV into the future

CdTe is a near perfect material for PV application with a direct band gap of ～1.5 eV that is closely matched to the terrestrial solar spectrum and a high optical absorption coefficient where less than 1 μm thickness is adequate to absorb the incident light. CdTe thin film solar cell and module technology has validated the economies of scale that were projected for thin film PV technologies since the early 1980s where manufacturing costs are now below $0.84 with module efficiencies of 11.1%. Additionally, the low-temperature coefficient of CdTe modules results in a high annualized output. A critical issue for CdTe manufacturers is that there is not a clear pathway to increase the module performance to 15% or beyond based on current laboratory results and efficiency improvements will require fundamental improvements in the CdTe semiconductor properties and/or developing an alternative device structure.     

Performance analysis of crystalline silicon solar modules with the same peak power and the different structure

Textured crystalline silicon solar cells, planar crystalline silicon solar cells, textured glass, and planar glass are commonly fabricated for crystalline silicon solar modules. Thus, there are four kinds of crystalline silicon solar modules. The photovoltaic electricity outputs of these four kinds of modules with the same peak power are different under true sunshine conditions. This discrepancy inevitably occurs due to the different materials used in modules. Using the actual optical performance of a four-layer encapsulation, a simulation was made on the reflection losses and energy outputs of the four kinds of solar modules. The computer simulation shows that the module encapsulated by textured crystalline silicon solar cells and textured glass has more energy output than others in actual uses. Even if they have equal electrical characteristics under standard test conditions of 1000 W/m², 25°C cell temperature, and 1.5 air mass, the result of simulation approximately agrees with the measured values. A quantitative analysis of energy production of the four kinds of modules with the same peak power as a function of angle of incidence and module structure is presented for the first time. Performing the measured energy production analysis for the four kinds of modules with the same peak power as a function of angle of incidence and module structure provides insight into economic analysis of PV systems and performance estimation of a photovoltaic roof within a fixed flat plate array.