All‐Polymer Bulk‐Heterojunction Enables Stable Monolithic Perovskite/Organic Tandem Solar Cells with High Efficiency

Perovskite-based tandem solar cells (PTSCs) are promising for achieving higher efficiency limits, making them promising candidates for energy supply. However, the commercialization in complex scenarios necessitate extreme stability and reliability of tandem devices, particularly in ambient conditions. Herein, the use of a high-efficiency and air-stable quaternary all-polymer bulk heterojunction (BHJ) is pioneered to optimize spectral absorption, facilitate charge transport, and suppress exciton recombination, resulting in 18.0% of power conversion efficiency (PCE) in the organic subcell. The resultant monolithic perovskite/organic tandem solar cell (POTSC) delivers an impressive PCE of 24.8%, with minimal efficiency distribution and negligible hysteresis. Ambient stability tests on tandem devices reveal outstanding ambient stability, which is attributed to the reduced increase in exciton recombination. Remarkably, the unencapsulated tandem device maintained 88% of its initial efficiency after exposure to air for 500 h. The superior stability is owing to the enhanced resistance of the hydrophobic all-polymer BHJ to water and oxygen, thereby protecting the perovskite active layer. This work provides a novel approach from an organic perspective for achieving superior efficiency and stability in POTSC devices and holds promise for future real-world applications in the field of tandem solar cells.