太阳能热光伏发电系统研究与仿真外文翻译[精品].doc

太阳能热光伏发电系统研究与仿真外文翻译 Introduction 11 Photovoltaic Energy Conversion 12 solar Cells and Solar Energy Conversion 13 solar Cell Applications References 11PHOTOVOLTAIC ENERGY CONVERSION Photovoltaic energy conversion is the direct production of electrical energy in the form of current and voltage from electromagnetic ie lightincluding infrared visible and ultraviolet energy The basic four steps needed for photovoltaic energy conversion are 1 a light absorption process which causes a transition in a material the absorber from ground state to an excited state the conversion of the excited state into at least a free negative and free positive-charge carriers pair and 3 discriminating transport mechanism which causes the resulting free negative-charge carriers to move in one direction to a con- tact that we will call the cathode and the resulting free positive- charge carriers to move in another direction to a contact that we will call the anode The energetic photogenerated negative-charge carriers arriving at the cathode result in electrons which travel through an external path an electric circuit While traveling this path they lose their energy doing something useful at an electrical load and finally they return to the anode of the cell At the anode every one of the returning electrons completes the fourth step of photovoltaic energy conversion which is closing the circle by 4 combining with an arriving positive-charge carrier thereby returning the absorber to the ground state In some materials the excited state may be a photogenerated free electron-free hole pair In such a situation step 1 and step 2 coalesce In some materials the excited state may be an exciton In which case steps 1 and 2 are distinct A study of the various man-made photovoltaic devices that carry out these four steps is the subject of this text Our main interest is photovoltaic devices that can efficie