Optical Effects of Thin Film Adhesives in Multijunction Solar Cells

摘要

Multijunction solar cells afford an attractive method of increasing module efficiency. The optical coupling of mechanically stacked cells 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 thin films between AlGaAs and Si cells are developed. An option currently being investigated for a series connected multijunction cell is illustrated. The multijunction cell with a multilayer optical coupling could have less than 1% reflectance loss between the cells. This compares most favorably to the approx.25% reflectance loss of thick adhesive layers, and approaches the reflectance of monolithic systems. (ERA citation 10:023635)