In 1997, a new 4 year plan was initiated in order to achieve more specific goals by FY 2000. An outline of the new 4 year program will be discussed with emphasis on Si thin film solar cells. The main objective of the program is to achieve stabilized efficiencies of over 10&percent; for large area a-Si based solar cell modules. In addition to amorphous Si based materials, polycrystalline and single crystal thin film Si has attracted attention as a low-cost solar cell material, where the target is to achieve 13-15&percent; efficiencies. Material and processing issues in the area of Si thin film solar cells will be briefly reviewed. ©1999 American Institute of Physics.