Semitransparent Perovskite Solar Cells for Building Integration and Tandem Photovoltaics: Design Strategies and Challenges

Over the past decade, halide perovskite systems have captured widespread attention among researchers since their exceptional photovoltaic (PV) performance is disclosed. The unique combination of optoelectronic properties and solution processability shown by these materials has enabled perovskite solar cells (PSCs) to reach efficiencies higher than 25% at low fabrication costs. Moreover, PSCs display enormous potential for modern unconventional PV applications, since they can be made lightweight, semitransparent (ST), and/or flexible by means of appropriate design strategies. In particular, by enabling transparency and high efficiency simultaneously, ST-PSCs hold great promise for future versatile utilization in the context of building-integrated PVs (BIPVs) or as top cells to be coupled with conventional lower-bandgap bottom cells in tandem PV devices. The present review aims to provide a detailed overview of latest research about ST-PSCs for BIPVs and tandems, by critically reporting on the most updated and effective design strategies in view of these two possible future applications. The differences and similarities between the available approaches are punctually highlighted, emphasizing the importance of a rigorous application-orientated ST-PSC design. Finally, the main challenges and issues about device design, operation, and stability that need to be addressed before commercialization are thoroughly scanned.