Cs<sub>4</sub> PbI<sub>6</sub> -Mediated Synthesis of Thermodynamically Stable FA<sub>0.15</sub> Cs<sub>0.85</sub> PbI<sub>3</sub> Perovskite Solar Cells.
basic_science · Level V
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- Record sourced from PubMed, PMID 32567102.
- Also identified by DOI 10.1002/adma.202001054.
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Abstract
The stability issue is still one of the main limitations of the commercialization of perovskite photovoltaics. The mixed cation FA<sub>x</sub> Cs<sub>1</sub> <sub>-x</sub> PbI<sub>3</sub> has shown great promise owing to its improved thermal and moisture stability. However, the study of FA<sub>x</sub> Cs<sub>1</sub> <sub>-x</sub> PbI<sub>3</sub> is concentrated on formamidine (FA)-rich perovskite, whereas cesium (Cs)-rich FA<sub>x</sub> Cs<sub>1</sub> <sub>-x</sub> PbI<sub>3</sub> perovskites are barely studied due to the inevitable phase separation when Cs > 30 mol%. Here, a Cs<sub>4</sub> PbI<sub>6</sub> -mediated method is developed to synthesize Cs-rich FA<sub>x</sub> Cs<sub>1</sub> <sub>-x</sub> PbI<sub>3</sub> perovskites. It is demonstrated that Cs<sub>4</sub> PbI<sub>6</sub> intermediate phase has a low Cs cation diffusion barrier and therefore offers a fast ion exchange with the preformed FA-rich perovskite phase to finally form the Cs-rich FA<sub>x</sub> Cs<sub>1</sub> <sub>-x</sub> PbI<sub>3</sub> perovskite. The results indicate that ≈15% alloying with organic FA cations can sufficiently stabilize the perovskite phase with excellent phase and UV-irradiation stability. The FA<sub>0.15</sub> Cs<sub>0.85</sub> PbI<sub>3</sub> perovskite solar cells achieve a champion power conversion efficiency of 17.5%, showing the great potential of Cs-based perovskites for efficient and stable solar cells.