Optical Effects of Thin Film Adhesives in Mechanically Stacked Multijunction Solar Cells

摘要

The use of multijunction solar cells allows an increased utilization of the solar spectrum and thereby increases cell efficiency. The optical coupling of cells with different bandgaps used in a mechanically stacked configuration, however, causes some concern since the gains from the bottom cell can be effectively negated by reflectance losses between the cells. A short outline of the theory of thin film optics as applied to this situation is presented. Theoretical reflectances of single and multiple layer adhesives between AlGaAs and Si cells are developed. An option currently being investigated for a series connected multijunction cell is illustrated. The multijunction cell with multilayer adhesives could have less than 2% reflectance loss between the cells. This compares most favorably to the 25% reflectance loss of thick adhesive layers. (ERA citation 11:002237)