Interconnect Junctions for Thin-Film Tandem Solar Cells

Polycrystalline thin-film, tandem solar cells promise high efficiencies and high open-circuit voltages. Along with the high-bandgap top cell, a thin-film interconnect junction is one of the more demanding components of a monolithic tandem. We will present electrical, optical, structural, and device-compatibility results from several interconnect junctions grown on Cu(In,Ga)Se₂, CdTe, and Si absorber layers. The physics of an interconnect junction will be discussed as a guide for choosing appropriate materials. Athough emphasis will be placed on several promising transparent p-type materials, results from degenerate n-type materials will also be discussed. Results of an n⁺/p⁺ interconnect junction in a monolithic tandem will be presented.