Modeling nipi solar cells under concentration accounting for state filling effects

Abstract

Significant development work has been completed in recent years to improve experimental results reaching a record efficiency of 9.14% under one sun AM0 conditions with no anti-reflection coating. The nipi solar cell utilizes epitaxial regrowth contacts to ensure carrier selective contacts to the alternating n and p-type doped layers, forming selectively ohmic and rectifying contacts. Defects or traps formed in the rectifying contact during the epitaxial regrowth process result in injected current that contributes directly to dark current. As a result detailed characterization of the epitaxial regrowth interface is required to understand and minimize the formation of interface traps. Concentration measurements have been completed to characterize the trap states impact on efficiency as higher concentration results in state filling and a recovery in open circuit voltage. A model has been developed to gain further understanding of the measurements under concentration.