Flexible all-perovskite tandem solar cells approaching 25% efficiency with molecule-bridged hole-selective contact

Lightweight flexible perovskite solar cells are promising for building integrated photovoltaics, wearable electronics, portable energy systems and aerospace applications. However, their highest certified efficiency of 19.9% lags behind their rigid counterparts (highest 25.7%), mainly due to defective interfaces at charge-selective contacts with perovskites on top. Here we use a mixture of two hole-selective molecules based on carbazole cores and phosphonic acid anchoring groups to form a self-assembled monolayer and bridge perovskite with a low temperature-processed NiO nanocrystal film. The hole-selective contact mitigates interfacial recombination and facilitates hole extraction. We show flexible all-perovskite tandem solar cells with an efficiency of 24.7% (certified 24.4%), outperforming all types of flexible thin-film solar cell. We also report 23.5% efficiency for larger device areas of 1.05 cm(2). The molecule-bridged interfaces enable significant bending durability of flexible all-perovskite tandem solar cells that retain their initial performance after 10,000 cycles of bending at a radius of 15 mm. The efficiency of flexible perovskite solar cells lags behind their rigid counterparts. Now, Li et al. devise a self-assembled monolayer bridged hole-selective contact with reduced defects and improved bending durability, achieving a 24.4% certified efficiency.

Automated summary

Lightweight flexible perovskite solar cells have great potential for various applications, but their efficiency lags behind rigid solar cells. In this study, a self-assembled monolayer bridged hole-selective contact with reduced defects and improved bending durability was developed, resulting in a certified efficiency of 24.4% for flexible all-perovskite tandem solar cells.