Growth rate of energy consumption is rising year after year in the world. Most of the energy comes from sources of petroleum, natural gas, windmill, geothermal, fossil-fuel, and nuclear power generation. These types of power generation systems are polluting, costly, or exhausted after all.

　　Thus, it is necessary to seek a renewable energy source to replace these power generation systems for the protection of our natural environment and future use. The sun has been radiating energy for over 500 million years, and is expected to continue for at least the next 50 million years. Thus, photovoltaic (solar) energy conversion is an excellent candidate for the renewal energy source because it is free, clean, inexhaustible, uninterruptible, and nonpolluting. Solar cells, which use the internal photovoltaic effect in a semiconductor, are capable of providing electricity directly from the sun for a wide variety of applications with the advantage of long-duration power generation at lower operating cost.

　　In recent years, a great deal of efforts has been devoted to the development of various low-cost, high-efficiency, and high-stability solar cells for both terrestrial and space power generation as well as for applications in consumer electronics. Cost and conversion efficiency are always the two key factors to determine the compatibility of a solar cell. Our researches focus on the development of both low-cost and high-efficiency photovoltaic devices.