Bifacial perovskite solar cells: a universal component that goes beyond albedo utilization.

Perovskite solar cells (PSCs) have achieved remarkable progress in the past decade and become the most powerful challenger of traditional silicon photovoltaics. Among the many designs, bifacial PSCs have received widespread attention these days due to their ability to fully utilize environmental reflection and scattering light to enhance energy yield. They also can provide better aesthetic design for building-integrated photovoltaics (BIPVs). However, the potential of bifacial PSCs is not limited to these traditional applications. Importantly, such architecture also serves as a universal component for multi-junction cells and photon engineering, which are both critical for further efficiency improvement. In this review, the requirements of different functional layers under various applications are described in detail, starting from the structure of bifacial PSCs. The application developments are introduced, including albedo utilization, semitransparent PSCs (ST-PSCs), TSCs. The present issues (such as stability, large area, recombination of carriers at the back electrode and toxicity etc.) and the extra challenges of bifacial PSCs are highlighted. It is hoped that this review can provide new ideas for the future development and further improve the competitiveness of PSCs.