Wide-bandgap organic–inorganic hybrid and all-inorganic perovskite solar cells and their application in all-perovskite tandem solar cells
The past decade has witnessed rapid development of perovskite solar cells (PSCs), the record power conversion efficiency (PCE) of which has been rapidly boosted from the initial 3.8% to a certified 25.5%, approaching the Shockley–Queisser (SQ) limit for single-junction solar cells. Tandem solar cells (TSCs) have gradually attracted more attention due to their great potential to break the SQ limit by reducing the thermalization losses. Among various kinds of perovskite-based tandems, all-perovskite TSCs offer great promise with the advantages of solution processability, low cost, and flexibility. As top cells for TSCs, the wide-bandgap (wide-Eg, >1.7 eV) PSCs play an essential role in harvesting the high-energy photons and providing high open-circuit voltage (Voc) for the multi-junction TSCs, which is helpful for maintaining the stability of the bottom cell by filtering harmful ultraviolet radiation. However, both organic–inorganic hybrid perovskites and all-inorganic perovskites encounter several problems, such as the phase instability and the large Voc deficits (Eg/q − Voc), which result in inferior performance of wide-Eg PSCs. Many efforts have been made to overcome the issues and researchers have already made encouraging progress. In this review, we summarize the recent progress on wide-Eg PSCs based on organic–inorganic hybrid perovskites and all-inorganic perovskites, as well as their application in all-perovskite TSCs. Finally, the main challenges and perspectives are discussed.