This research program is directed toward the advancement of understanding of amorphous silicon-based alloys and their use in small area multi-junction solar cells. The principal objectives of the program are: (i) to develop a broad scientific base for the chemical, structural, optical and electronic properties of amorphous silicon-based alloys; (ii) to determine the optimum properties of these alloy materials as they relate to high efficiency cells; (iii) to determine the optimum device configuration for multi-junction cells; and (iv) to demonstrate by the end of February, 1990 the proof-of-concept multi-junction amorphous silicon alloy-based solar cells having an efficiency of 16% under standard global AM1.5 solar insolation conditions and having an area of at least 1 cm{sup 2}. 23 refs., 49 figs., 10 tabs.