Fig. 6. Tuning the spectra via anion and cation engineering.

a PL spectra of 3D perovskite films with various contents of Cl ions. b Temperature-dependent conductivity measurement for different perovskite films to obtain the activation energy of ion migration. c EL spectra of control and DPPOCl-treated quasi-2D PeLEDs. Inset: Schematic representation of Cl ion insertion and immobilization in DPPOCl-treated perovskites. d UV-vis absorption and PL spectra of PEA₂(Rb_xCs_1−x)₂Pb₃Br₁₀ perovskites with various contents of Rb ions (0 ≤ x ≤ 1). e Calculated electronic density of states (DOS) of control and EABr-treated perovskites. f PL spectra for different EABr contents. Panel a is reprinted from ref. ⁹⁷ with permission from Springer Nature. Panel b is reprinted from ref. ¹⁰² with permission from Springer Nature. Panel c is reprinted from ref. ¹⁰⁴ with permission from the American Chemical Society. Panel d is reprinted from ref. ¹¹⁰ with permission from Springer Nature. Panels e, f are reprinted from ref. ⁴⁵ with permission from Springer Nature