Fig. 1. Morphologies and XRD patterns of perovskite films with different doping concentrations of HPA, where the insets are high-resolution SEM images. (a) Doping concentration of HPA is 0; (b) doping concentration of HPA is 5%; (c) doping concentration of HPA is 10%; (d) doping concentration of HPA is 20%; (e) XRD patterns

Fig. 2. Characteristics of perovskite films with different doping concentrations of HPA. (a) Absorption spectra; (b) photoluminescence spectra; (c) TRPL characteristics; (d) current-voltage characteristics of hole-dominated devices; (e) Fourier transform infrared spectra of PbBr₂, HPA, and PbBr₂+HPA samples

Fig. 3. Characteristics of perovskite light-emitting devices with different doping concentrations of HPA. (a) Device structure; (b) current density-luminance-voltage characteristics; (c) electroluminescent spectra; (d) external quantum efficiency (EQE)-voltage characteristics; (e) CIE coordinates of devices with HPA doping concentration of 10%

Fig. 4. Features of light-emitting devices. (a) EL spectra of devices without HPA doping; (b) EL spectra of device with HPA doping concentration of 10% under different voltages; (c) operational lifetime of devices with HPA doping concentration of 0 and 10% with an initial luminance of 100 cd/m²