The development of a low-cost but efficient photovoltaic device has been a prime goal of recent research.1 Achieving the Department of Energy's cost objectives probably requires a technology based on either polycrystallilne or amorphous thin films. It is doubtful that single-crystal technology will be cost-competitive for the one-sun residential flat-plate collector application in the forseeable future. In order to meet efficiency goals, devices have been designed to circumvent the expected short lifetimes and diffusion lengths of polycrystalline materials. In such materials, one expects the grain surfaces to be efficient recombination sites. Therefore, the minority carrier diffusion length may be limited to about a one-grain diameter, which typically is about one micron or less in evaporated films.