Autumn is the most beautiful season in Beijing.At this time, the World Horticultural Exposition in Yanqing, Beijing, has a unique view.Under the shade of flowers and trees, the landmark building - China Pavilion looks like a wishful handle, the whole building is magnificent, and the architectural style is full of Chinese characteristics. What interests reporters more is the "green technology" atmosphere of the whole China Pavilion.

   It is understood that the China Pavilion is a green building known as "breathing and living", with solar photovoltaic panels on the roof; the combination of glass curtain wall and membrane structure forms a thermal insulation layer, which can reduce the energy consumption of building heating and cooling.

   According to Kai Cui, design director of China Pavilion of Beijing World Horticultural Exposition and academician of Chinese Academy of engineering, 1024 CdTe thin film color transparent photovoltaic glass are installed on the steel structure roof of China Pavilion, which has higher light absorption efficiency and can better adapt to the shape trend of buildings.The transparent color of the CdTe film module on the roof has a light transmittance of 40% and different sizes. The color of the module is the traditional golden yellow in China, forming a semi-circular Ruyi shape with unique oriental charm. And it is the products of Adanced Solar Power.(hereinafter referred to as ASP) that perfectly realizes Kai Cui's "low carbon, ecological and green" design concept.

   "CdTe thin film color transparent photovoltaic glass" concept, which makes the reporter very novel, so came to ASP in Hangzhou Economic and Technological Development Zone for in-depth interview.

  After visiting the production workshop and product exhibition room of ASP, the reporter has a preliminary understanding of ASP. ASP was founded in 2008 by Xuanzhi Wu, an International Photovoltaic expert. It has been committed to the industrialization of high efficiency CdTe thin film solar cell technology in China.

  Since May 2008, after three and a half years of efforts, ASP has successively established experimental lines, pilot lines and production lines. It has gone through various stages from the development of small area batteries in the laboratory to the development of small components, until the production of large area components of 1.2m × 0.6m,The company has developed a complete set of production process and core equipment of CdTe modules with independent intellectual property rights, established a fully automatic, national production and design capacity of 40mW CdTe thin film solar cell module production line, and more than 40 production equipment on the line have been localized. At the same time, the new battery structure, new materials (new buffer layer, window layer and back electrode) developed by ASP and large area CdTe thin film deposition technology by improved short-range sublimation (CSS) are used in the production line for the first time.

  In the company, the reporter met Gang Bao, director of energy marketing of Longyan, who introduced the application of CdTe thin film photovoltaic module in the China Pavilion project.

 ASP makes use of its own technical advantages, empowers buildings with technology and helps the construction of China Pavilion, which is a model of green and sustainable development of the Expo.On the one hand, it has the functions of maintenance, heat insulation and beauty of common transparent roof and curtain wall, and has the power generation function, realizing the green building concept from passive energy saving to active power generation; On the other hand, it not only ingeniously combines with the roof and curtain wall components of the building, the products are made into different sizes, different transmittance and different colors according to the special requirements of China Pavilion, perfectly replacing the traditional curtain wall glass, and truly realizing photovoltaic glass instead of building glass.

   According to Gang Bao, at present, the photovoltaic technology mastered by human beings has strong material properties, that is, the absorption material is the fundamental factor determining the performance of photovoltaic cell devices. Compared with crystal silicon technology, which is the mainstream technology in the market, cadmium telluride absorbs 100 times more light than silicon material and is a stable binary compound, CdTe thin film solar cells are very suitable for large-scale production, and the production process of CdTe thin film solar cells makes its industrial chain shorter, so it is easier to achieve cost control in the production process; Because of its better performance of low light, temperature coefficient and anti blocking, the final module products have a wider range of applicable scenarios, which can play a very important role in building photovoltaic integration. The CdTe thin film photovoltaic cell technology has achieved an accumulated installed capacity of more than 20GW and an annual output of more than 3GW in 2015, driven by the First Solar energy company, a well-known photovoltaic enterprise in the United States.

   "Although CdTe solar cell technology has a good development prospect, its core technology has been monopolized by foreign advanced enterprises for a long time," said Gangbao. Real and good core technology can't be bought back with money. We must rely on independent innovation to develop. In the process of industrialization, we have encountered many difficulties. After 10 years of efforts and hard work, we have finally realized the leap from Made in China to Created in China. Through independent innovation and mastering a complete set of core technologies, the industrialization of CdTe thin film solar cell technology has been realized in China. " At present, the power generation capacity of CdTe thin film module products produced by Longyan energy is strong, and the conversion efficiency is over 14%, which has entered the world advanced level; The temperature coefficient of CdTe battery is about -0.21%/℃, less than half of that of crystalline silicon battery,In addition, the long strip sub battery can reduce the hot spot effect, improve the power generation capacity, ensure the product life and use safety; in the manufacturing process, due to the precise control of temperature, the damage rate of components is very small.

   When it comes to the advantages of CdTe thin film technology, Bao believes that the progress of CdTe thin film technology will promote the reduction of the cost of kilowatt hour electricity, and then realize realize power parity online. In terms of environmental protection, ASP can recover more than 80% of the waste resources of tellurium and cadmium. He said that the green and recycling advantages of cadmium telluride are incomparable with other technologies.

Gang Bao said that ASP always adheres to its own evaluation standard for the quality of a photovoltaic technology, that is, "Four High and One Low". "Four Highs" refers to high efficiency, high stability, high yield and high rate of good products, "One Low" refers to low cost. At present, in terms of thin-film photovoltaic technology, copper indium gallium selenium can be used to prepare batteries with very good performance due to its material characteristics; however, due to the scarcity of raw materials and the fact that it is a quaternary compound at the same time, to prepare large-area and uniform composition of thin-film semiconductor devices, its requirements for production equipment are higher and the process is more complex. Because the yield and yield rate are always a contradiction that can't be solved, which leads to its cost lagging behind than market development. However, the cost of GaAs technology is higher. At present, GaAs technology is only suitable for high-end applications such as aerospace, and cannot be promoted on a large scale temporarily.In contrast, CdTe has the value of large-scale commercialization. "At present, under the condition of low efficiency and small scale, the cost of CdTe thin film technology of our company is less than 30 cents (RMB 2), which is close to the world leading level: the efficiency of mass production components of the first production line mentioned above is about 14%, and the capacity is more than 30 megawatts." Gangbao said proudly.

   In order to give full play to its unique advantages of CdTe technology and realize BIPV, ASP began to layout building photovoltaic integration as early as four years ago. At present, ASP has developed a large number of new photovoltaic building components, such as photovoltaic thermal insulation module, photovoltaic water heater, photovoltaic hollow glass window, large-area photovoltaic light transmitting floor window, as well as more than 20 new products, such as transmittance, pattern, color, shape and size, which can be customized according to customer requirements. The CdTe thin film module products of ASP have covered all provinces, autonomous regions, Hong Kong, Macao and Taiwan, and are sold to 38 countries and regions in the world. It has been applied to the external structures of many landmark green buildings at home and abroad, such as Datong future energy Museum, National Theatre Dance Center, Jiaxing Photovoltaic Science and Technology Museum, London Canary Wharf bus station, Dutch hospital, etc., showing its unique market competitiveness and comprehensive application value.