Thin tantalum–silicon–oxygen/tantalum–silicon–nitrogen films as high-efficiency humidity diffusion barriers for solar cell encapsulation

Abstract

Flexible thin-film solar cells require flexible encapsulation to protect the copper–indium–2 selenide (CIS) absorber layer from humidity and aggressive environmental influences. Tantalum–silicon-based diffusion barriers are currently a favorite material to prevent future semiconductor devices from copper diffusion. In this work tantalum–silicon–nitrogen (Ta–Si–N) and tantalum–silicon–oxygen (Ta–Si–O) films were investigated and optimized for thin-film solar cell encapsulation of next-generation flexible solar modules.CIS solar modules were coated with tantalum-based barrier layers. The performance of the thin-film barrier encapsulation was determined by measuring the remaining module efficiency after a 1000 h accelerated aging test. A significantly enhanced stability against humidity diffusion in comparison to non-encapsulated modules was reached with a reactively sputtered thin-film system consisting of 250 nm Ta–Si–O and 15 nm Ta–Si–N.