Nanoscale Rear‐Interface Architecture Enables 36.2 mA cm ⁻² Photocurrent in Ultrathin and Bifacial ACIGS Solar Cells Through Light Management

ABSTRACT Reducing the absorber thickness in thin‐film photovoltaics has a direct impact on low raw material consumption and high manufacturing throughput. However, it leads to low optical performance due to incomplete light absorption. In (Ag,Cu)(In,Ga)Se 2 (ACIGS)‐based technology, this limitation has been manifested in a photogenerated current density gap between standard and ultrathin devices, hindering their competitiveness and scalability. In this study, it is demonstrated that the optical performance gap of ultrathin ACIGS solar cells to standard devices can be closed by implementing a scalable light management structure at the rear contact. The core of such advancement is a nanoscale‐structured SiO x periodic array, designed on a transparent rear contact through optical simulations to promote light scattering and increase the optical path length inside the absorber, and developed by a suitable nanoimprint lithography process. This strategy enables 500–600 nm ACIGS solar cells to reach a short‐circuit current density of 36.2 mA cm −2 , surpassing 80% of the Shockley–Queisser limit, which has not been reported for such ultrathin devices. The proposed architecture provides gains in bifacial configuration. This way, a fundamental performance limitation of ultrathin solar cells is overcome, enabling material‐efficient and integrated photovoltaic applications.