Decoupling the effects of defects on efficiency and stability through phosphonates in stable halide perovskite solar cells

Understanding defects is of paramount importance for the development of stable halide perovskite solar cells (PSCs). However, isolating their distinctive effects on device efficiency and stability is currently a challenge. We report that adding the organic molecule 3-phosphonopropionic acid (H3pp) to the halide perovskite results in unchanged overall optoelectronic performance while having a tremendous effect on device stability. We obtained PSCs with ∼21% efficiency that retain ∼100% of the initial efficiency after 1,000 h at the maximum power point under simulated AM1.5G illumination. The strong interaction between the perovskite and the H3pp molecule through two types of hydrogen bonds (H…I and O…H) leads to shallow point defect passivation that has a significant effect on device stability but not on the non-radiative recombination and device efficiency. We expect that our work will have important implications for the current understanding and advancement of operational PSCs. [Display omitted] •Phosphonates interact strongly with halide perovskites through hydrogen bonds•Deep defect passivation and non-radiative recombination remain unaffected•Shallow point defect passivation and ion immobilization result in high device stability•Nearly 100% of the initial efficiency (21%) is retained after 1,000 h of illumination Shallow defects, which are considered benign in classical inorganic semiconductors, result unfavorably for ionic-electronic conductors such as halide perovskites, causing ion migration and poor operational stability when applied in a solar cell. We report that the organic molecule 3-phosphonopropionic acid (H3pp), added to the halide perovskite, passivates shallow point defects having minimal effect on deep-defect passivation and non-radiative recombination. This results in an unaffected overall optoelectronic performance while having a tremendous effect on the stability of the perovskite solar cell. The hydrogen binding modes benefits the immobilization of ions that leads to the exceptional operational stability. Our findings permit decoupling of the effects of defects on efficiency and stability to advance in the understanding of the relation between shallow and deep-defect passivation, non-radiative recombination, and PSC performance. The organic molecule 3-phosphonopropionic acid (H3pp) interacts strongly with the halide perovskite through two types of hydrogen bonds (H…I and O…H). This binding mode results in shallow point defect passivat