Stability of plasmonic metal nanoparticles integrated in the back contact of ultra-thin Cu(In,Ga)S2 solar cells

► We prove the stability of metal nanoparticles in a transparent solar cell back contact. ► Ag nanoparticles are integrated in a Cu(In,Ga)S2 solar cell. ► Absorption enhancement is found in optical properties. ► A 6.9% efficient Cu(In,Ga)S2 solar cell with 500 nm absorber thickness is shown. ► Further proof of plasmonic enhancement requires ultra-thin devices.