Tetrafluoride anion substitution and its role on performance enhancement in quasi-2D perovskite light-emitting diode

Pseudo-halide substitution is an effective approach to enhance the performance and stability of perovskite optoelectronic devices. However, the role of pseudo-halide ions played in the perovskite light-emitting diodes (PeLEDs) is still rarely investigated. Herein, we have synthesized the organic salt PEABF₄ (PEA = phenylethylamine) as a pseudo halide substitute for surface halides in PEABr and fabricate quasi two-dimensional (quasi-2D) PeLEDs. The incorporation of BF₄⁻ anion improves the photoluminescence (PL) intensity and lifetime by taking advantage of improved crystallinity and enlarged grain size. The BF₄⁻ substituted PeLEDs shows great improvement of performance to the control devices. The optimized device with structure of indium tin oxide-coated glass (ITO(glass))/poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate)(PEDOT:PSS)/perovskite/4,7-Diphenyl-1,10-phenanthroline (Bphen)/Ag produces a maximum luminance at 44850 cd/m², and an efficiency of 11.5 cd/A, respectively. Through further investigation by optical and electrical characterization, we find the substitution of BF₄⁻ anion has merits on the enhancement of exciton binding energy and suppression of non-radiative trap-assisted recombination on the surface. These results provide better understanding of pseudo-halide's benefits in perovskite light-emitting devices.