Enhancing the Phase Stability of Formamidinium Lead Triiodide by Addition of Calcium Chloride

Abstract

Formamidinium lead triiodide (FAPbI 3 ) with stable black perovskite phase and without significantly changing its bandgap is demonstrated by the incorporation of CaCl 2 . More incorporated CaCl 2 in FAPbI 3 creates a desirable crystal structure, satisfying the Goldschmidt tolerance factor, and thereby stabilizing black perovskite phase under ambient conditions. However, more incorporated CaCl 2 in FAPbI 3 is likely to degrade the perovskite due to its hygroscopic characteristics. In addition, the incorporated CaCl 2 in FAPbI 3 solution reduces solubility, causing the formation of smaller crystal grains and pinholes due to quick precipitation during the non-solvent dripping crystallization process. Accordingly, 5 % CaCl 2 incorporated FAPbI 3 films have the best phase stability and solar cell performance with 18.0 % of power conversion efficiency at 1 sun condition.

Performance Improvement of Lead‐Based Halide Perovskites through B‐Site Ion‐Doping Strategies

“…[84] As mentioned earlier, small cations are often used to replace Pb 2+ at the B-site to reduce the lattice constant, optimize the tolerance factor, and improve the performance of the device. [16,77,92] Higher doping concentrations are better for the tolerance factor. However, this is not the case.…”

“…After aging at 20 °C and 20% relative humidity for 500 h, the efficiency of the optimized sample decreased by 26.72% while that of the undoped sample decreased by 97.42%. [ 92 ] Additionally, Yao and co‐workers indicated that the average grain size of CsPbI 3 perovskite film with or without Mn addition was ≈350 nm (0%), ≈563 nm (2%), and ≈479 nm (4%). The lifetime of the champion carrier was 5.84 ns for the CsPbI 3 film doped with 2%, about twice that of 0% (2.99 ns).…”