20.67%-Efficiency Inorganic CsPbI3 Solar Cells Enabled by Zwitterion Ion Interface Treatment.

All-inorganic CsPbI3 perovskite solar cells (PSCs) have been extensively studied due to their high thermal stability and unprecedented rise in power conversion efficiency (PCE). Recently, the champion PCE of CsPbI3 PSCs has reached up to 21%; however, it is still much lower than that of organic-inorganic hybrid PSCs. Interface modification to passivate surface defects and minimize charge recombination and trapping is important to further improve the efficiency of CsPbI3 PSCs. Herein, a new zwitterion ion is deposited at the interface between electron transporting layer (ETL) and perovskite layer to passivate the defects therein. The zwitterion ions can not only passivate oxygen vacancy (VO ) and iodine vacancy (VI ) defects, but also improve the band alignment at the ETL-perovskite interface. After the interface treatment, the PCE of CsPbI3 device reaches up to 20.67%, which is among the highest values of CsPbI3 PSCs so far. Due to the defect passivation and hydrophobicity improvement, the PCE of optimized device remains 94% of its original value after 800 h storing under ambient condition. These results provide an efficient way to improve the quality of ETL-perovskite interface by zwitterion ions for achieving high performance inorganic CsPbI3 PSCs.

21.15%-Efficiency and Stable γ -CsPbI3 Perovskite Solar Cells Enabled by an Acyloin Ligand.

Cesium lead triiodide (CsPbI3 ) is a promising light-absorbing material for constructing perovskite solar cells (PSCs) owing to its favorable bandgap and thermal tolerance. However, the high density of defects in the CsPbI3 film not only act as recombination centers, but also facilitate ion migration, leading to lower PCE and inferior stability compared with the state-of-the-art organic-inorganic hybrid PSC counterpart. Theoretical analyses suggest that the effective suppression of defects in CsPbI3 film is helpful for improving the device performance. Herein, the stable and efficient γ -CsPbI3 PSCs are demonstrated by developing an acyloin ligand (1,2-di(thiophen-2-yl)ethane-1,2-dione (DED)) as a phase stabilizer and defect passivator. The experiment and calculation results confirm that carbonyl and thienyl in DED can synergistically interact with CsPbI3 by forming a chelate to effectively passivate Pb-related defects and further suppress ion migration. Consequently, DED-treated CsPbI3 PSCs yield a champion PCE of 21.15%, which is one of the highest PCE among all the reported CsPbI3 PSCs to date. In addition, the unencapsulated DED-CsPbI3 PSC can retain 94.9% of itsinitial PCE when stored under ambient conditions for 1000 h and 92.8% of its initial PCE under constant illumination for 250 h.