Cu(In,Ga)Se-2 based ultrathin solar cells the pathway from lab rigid to large scale flexible technology

Abstract

The incorporation of interface passivation structures in ultrathin Cu(In,Ga)Se-2 based solar cells is shown. The fabrication used an industry scalable lithography technique-nanoimprint lithography (NIL)-for a 15 x 15 cm(2) dielectric layer patterning. Devices with a NIL nanopatterned dielectric layer are benchmarked against electron-beam lithography (EBL) patterning, using rigid substrates. The NIL patterned device shows similar performance to the EBL patterned device.The impact of the lithographic processes in the rigid solar cells' performance were evaluated via X-ray Photoelectron Spectroscopy and through a Solar Cell Capacitance Simulator. The device on stainless-steel showed a slightly lower performance than the rigid approach, due to additional challenges of processing steel substrates, even though scanning transmission electron microscopy did not show clear evidence of impurity diffusion. Notwithstanding, time-resolved photoluminescence results strongly suggested elemental diffusion from the flexible substrate. Nevertheless, bending tests on the stainless-steel device demonstrated the mechanical stability of the CIGS-based device.