Suppressing Metal Cation Diffusion in Perovskite Light-Emitting Diodes via Blending Amino Acids with PEDOT:PSS

Abstract

While the migration of halide anions in the perovskite lattice has been extensively studied owing to the undesirable shifts in the emission spectrum of perovskite light-emitting diodes (PeLEDs), the diffusion behavior of doped metal cations in perovskite crystals during device operation remains hitherto unexplored. Therefore, gaining a deep understanding and developing mitigation strategies for ion migration are crucial to achieving the full potential of the PeLED technology. In this study, we analyzed the feasibility of using of amino acids as interlayer additives in poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) to block metal cation migration and passivate surface defects in Na⁺-doped CsPbBr₃ films. We systematically selected and analyzed a series of amino acids (l-leucine, l-lysine, and l-glutamine) and found that blending PEDOT:PSS with l-lysine significantly suppressed Na⁺ diffusion and enhanced the external quantum efficiency (EQE) of the CsPbBr₃ PeLEDs. This result was attributed to the chelating ability of l-lysine with amine and carboxyl groups, which form strong coordination bonds with the metal cations. Furthermore, the l-lysine with two amine groups improved the crystallization quality of CsPbBr₃ films with reduced surface roughness and improved surface passivation, leading to increased photoluminescence quantum yields. Overall, the modified CsPbBr₃ PeLEDs with l-lysine-blended PEDOT:PSS exhibited much improved device performance, such as EQE and luminance. Our results provide insights into the role of amino acid additives in enhancing the performances and stabilities of perovskite-based optoelectronic devices.