Fig. 1. Synthesis of PEA_xCsPbBr_3–yCl_y + PEG + KBr based perovskite precursor solution

Fig. 2. SEM images of PEA_xCsPbBr_3-yCl_y perovskite films with different additives, the scale bar is 200 nm

Fig. 3. Histograms of grain size distributions of PEA_xCsPbBr_3-yCl_y perovskite films with different additives.

Fig. 4. XRD patterns of various PEA_xCsPbBr_3-yCl_y perovskite films with different additives on PEDOT:PSS.

Fig. 5. Optical characterization of PEA_xCsPbBr_3–yCl_y perovskite films with different additives: (a) PL spectroscopy; (b) PLQY; (b) TRPL decay curves.

Fig. 6. (a) Device structure diagram of PeLEDs; (b) Cross-sectional SEM images of PeLEDs

Fig. 7. Electrical performance characteristics of PeLEDs with different additives: (a) Current density-voltage-luminance(J-V-L); (b) current efficiency-current density-external quantum efficiency(CE-J-EQE); (c) the normalized EL spectra; (d) the Commission Internationale de I’Eclairage (CIE) coordinates

Fig. 8. (a) Operating lifetime characteristics of PeLEDs with different additives. The corresponding EL spectra of PeLEDs with different additives at T₀ and T₅₀: (b) Control; (c) with PEG; (d) with PEG+KBr

Fig. 9. The spectral stability of PeLEDs: (a) Control; (b) with PEG; (c) with PEG + KBr.

Fig. 10. The EL spectra of PeLEDs with different working minutes at 5.7 V: (a) Control; (b) with PEG; (c) with PEG+KBr.