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版權所有 翻印必究 指導教授:林克默 博士 日 期:2011.05.02 報 告 人:王禮國 Abstract 版權所有 翻印必究 • Three decades of research has led to the discovery of new materials and devices and new processing techniques for lowcost manufacturing. This has resulted in improved sunlight-toelectricity conversion efficiencies, improved outdoor reliability, and lower module and system costs. • This paper reviews the significant progress that has occurred in PV materials and devices research over the past 30 years, focusing on the advances in crystal growth and materials research, and examines the challenges to reaching the ultimate potential of current-generation (crystalline silicon), next-generation (thin films and concentrators), and future-generation PV technologies. • The latter includes innovative materials and device concepts that hold the promise of significantly higher conversion efficiencies and/or much lower costs. 2010/10/29 STUT 太陽能材料與模組實驗室 2 版權所有 翻印必究 Introduction • The principal materials issue in PV then is the growth of the semiconductor materials and layers, including conventional materials such as silicon, gallium arsenide, and cadmium telluride, and newer materials such as copper indium diselenide, hydrogenated amorphous silicon, and various ternary and multinary III–V, II–VI, and I–III–VI alloy materials • These multijunction cells are able to utilize the solar spectrum more efficiently. 2010/10/29 STUT 太陽能材料與模組實驗室 3 Historical trends of success 版權所有 翻印必究 • One of the most significant trends is the continuous improvement of solar cell efficiencies for all technologies 2010/10/29 STUT 太陽能材料與模組實驗室 4 版權所有 翻印必究 PV technology options • Photovoltaic technologies can be divided into two main areas: flat plates and concentrators. • Flat- plate technologies include crystalline silicon and thin films of various materials, usually deposited on some low-cost substrate, such as glass, plastic, or stainless steel, using some type of vapor deposition, electrodeposition, or wet-chemical process. • Thin-film cells typically require onetenth to one-hundredth of the expensive semiconductor material required by crystalline silicon. • A system of lenses or reflectors made from lessexpensive materials is used to focus sunlight on smaller, somewhat more expensive, but highly efficient solar cells. 2010/10/29 STUT 太陽能材料與模組實驗室 5 版權所有 翻印必究 Flat-plate crystalline silicon • • • • Silicon feedstock Ingot-based technologies Noingot-based technologies High-efficiency silicon solar cells 2010/10/29 STUT 太陽能材料與模組實驗室 6 版權所有 翻印必究 Flat-plate thin films • Thin-film technologies have the potential for substantial cost advantage versus wafer-based c-Si because of factors such as lower material use (due to direct bandgaps), fewer processing steps, and simpler manufacturing technology for large-area modules. Many of the processes are high throughput, continuous (e.g., roll-to-roll), usually do not involve high temperatures, and, in some cases, do not require high-vacuum deposition equipment. The process of module fabrication, involving the interconnection of individual solar cells, is usually carried out as part of the filmdeposition processes. 2010/10/29 STUT 太陽能材料與模組實驗室 7 版權所有 翻印必究 • • • • • • Amorphous silicon Cadmium telluride Copper indium diselenide(CIGS) Polycrystalline thin-film multijunctions Thin crystalline silicon Transparent conducting oxides 2010/10/29 STUT 太陽能材料與模組實驗室 8 版權所有 翻印必究 Concentrators • Silicon concentrator cells • The key elements of a concentrator PV system are low-cost concentrating optics, low-cost mounting and tracking systems, and high-efficiency (and relatively low-cost) solar cells. • First, most of today’s remote and distributed markets for PV systems are not suitable for concentrator systems. Second, concentrator systems use only direct (rather than diffuse or global) solar radiation, and therefore their areas of best application are limited compared to flat plates.and relatively lowcost) solar cells. 2010/10/29 STUT 太陽能材料與模組實驗室 9 版權所有 翻印必究 結論 • 為降低生產成本進行許多研究，導致許多新技術與材料應用 意外的發展與應用，例如染料敏化電池等，皆是研究代表。 • 研究光伏到現今為止，大部分的研究，主要是晶體生長和材 料的發展，未來仍是主要方向。 • 晶圓製程基礎與矽晶體製程技術（包括矽錠），將繼續主導 太陽能模組產業未來十年的發展，也許更長的時間。 • 現階段模組價格趨於穩定，保持不變的25％年均增長率，預 計直到2050年以後，石油能源枯竭，綠能將更加重要，這將 導致光伏市場不斷擴大。 2010/10/29 STUT 太陽能材料與模組實驗室 10 版權所有 翻印必究 Thank you for your attention 2011/3/22 11 版權所有 翻印必究 Ingot-based technologies • The highest-efficiency silicon solar cells to date (e.g., 24.7% in Fig. 1) were made using singlecrystal, float-zone (FZ) silicon, but the commercial use of FZ silicon for PV has started only recently. • Using its back-contact solar cell, SunPower achieved 21.5% efficiency with high-lifetime, n-type FZ silicon wafers [3]. • Topsil is now developing high-volume production of lowercost FZ wafers for solar cells [4]. Faster growth rates and the ability to use lower-cost, irregular polysilicon feedrods are expected to result in lower costs. There are many new opportunities for crystal growth developments in this area. 2010/10/29 STUT 太陽能材料與模組實驗室 12 版權所有 翻印必究 Ingot-based technologies 2010/10/29 STUT 太陽能材料與模組實驗室 13 版權所有 翻印必究 Noingot-based technologies • Silicon ribbon or sheet technologies, which avoid the costs and material losses associated with slicing ingots, have been at the forefront of terrestrial PV development. • The field has been ripe with crystal growth innovations, and, out of the more than 20 techniques researched over the past 30 years, several have become the first of the new PV technologies to be commercialized. 2010/10/29 STUT 太陽能材料與模組實驗室 14 版權所有 翻印必究 High-efficiency silicon solar cells • Most experts agree that the key to continued progress in c-Si PV is in improving cell and module efficiencies (as well as reducing module manufacturing costs). • Material quality ultimately relates back to the crystal growth processes where the controls of defects and impurities can be best effected. A critical process step for all polycrystalline silicon solar cells is the plasma-enhanced CVD of silicon nitride (from SiH4 and NH3) after p–n junction formation [8]. The SiNx:H layer not only forms an anti-reflective layer, it results in the passivation of defects and impurities by hydrogen diffusion during deposition and annealing. 2010/10/29 STUT 太陽能材料與模組實驗室 15