The development of a polycrystalline, thin-film solar cell utilizing a heterojunction structure based upon N-type CdS and P-type CuInSe2 semiconductor materials is described. The cell, prepared entirely by vacuum deposition and sputtering techniques onto inexpensive substrates, has potential applications as a low-cost mass produced device for photovoltaic power generation systems. A device efficiency of 7.5% under simulated AM-1 illumination is reported. Material and device properties pertinent to the development of the high efficiency cell are reviewed. The electrical, optical, and structural properties of the deposited thin-film materials are described. Results of detailed cell characterization using a variety of electrical, optical, and thermal measurements are presented and analyzed in terms of a photovoltaic cell model dominated by interface state recombinations. Finally, the projected, realistically achievable performance of this thin-film cell is discussed.