Amorphous Silicon Solar Cells / Amorphous Photosensors 2007-11The Concept Behind Solar Cell Power Generation Solar cell power is generated using the photovoltaic effect of Light semiconductors. When a semiconductor is exposed to a light source Transparent of suitable intensity, a large number of pairs of an electron and a electrode + + + p + + positive hole are generated as a result of the reciprocal action + + + + + + + + + + - + - between photons and silicon atoms. + i - - + - + + At a p/n junction between two different semiconductor materials, the + - - - - n - - - - - - - electrons are diffused in the n-type material and the positive holes - Metal - - - - - - - Electron - electrode are scattered in the p-type material. They are then collected at both + Positive hole electrodes respectively, resulting in a voltage difference between the electrodes. When an external load is connected, electricity flows through the load. In this way, an a-Si solar cell converts light energy into electricity and supplies power to external loads. Amorphous Silicon Solar Cells Solar cells are classified according to the material employed, i.e., crystal silicon, amorphous silicon, and compound semiconductor solar cells.Amorphou refers to objects having no definite shape and is defined as non-crystal material. Unlike crystal silicon, in which atomic arrangements are regular, amorphous silicon features irregular atomic arrangements as shown in the figures below. As a result, the reciprocal action between photons and silicon atoms occurs more frequently in amorphous silicon than in crystal silicon, allowing much more light to be absorbed. Thus, an ultra- thin amorphous silicon film of less than 1m can be produced and used for power generation. Also, by utilizing metal or plastics for the substrate, flexible solar cells can be produced. Amorton is an integrated amorphous silicon solar cell which has been developed by SANYO. Amorton uses silane (SiH4) as its source gas and is fabricated using a plasma CVD method. Three amorphous silicon layers p-layer, i-layer, and n-layer are formed consecutively on a glass substrate. This p-i-n junction corresponds to the p/n junction of a crystal silicon solar cell. In the process of this junction formation, a number of cells are connected The development of the solar cell is progressing with rapid speed. in series on a substrate at one time. This allows any As a new energy tool which can effectively harness the amazing power of sunlight, desired voltage to be obtained for a variety of equipment operation. solar cells have the potential to replace fossil fuels as our main means of power generation. Amorphous Crystal Solar energy is both a clean and inexhaustible resource, and it can be used to produce electricity wherever and whenever sunlight is available. Of these technologies, amorphous silicon solar cells have many strengths that surpass those of the earlier crystalline silicon solar cells. In addition, they require little energy to manufacture and use less raw materials, and thus are truly environmentally friendly devices. This technology also allows larger area cells to be manufactured and can take advantage of the flexibility of thin film materials, and they have already been used in a wide range of applications. SANYO was one of the first companies to focus on amorphous silicon solar cells, and developed and is now mass producing the Amorton integrated type amorphous silicon solar cells that feature a new device structure. 1 2 Load Electric current