Highly flexible and stable green perovskite light-emitting diodes based on IL-modified PEDOT:PSS film

Abstract

Flexible light-emitting diodes (LEDs) are highly sought-after for various applications, such as wearable medical devices, decorative lighting, and flexible displays. Perovskite-based LEDs, due to their low cost, ease of fabrication, and high color purity, have attracted significant attention as promising candidates for modern display technology. However, a primary challenge remains in selecting a bottom anode that provides both high electrical conductivity and optical transmittance while maintaining mechanical robustness to endure rigorous bending. To address this issue, a highly flexible and stable ionic liquid (IL)-modified poly(3,4-ethylene dioxythiophene) polystyrene sulfonate (PEDOT:PSS) bottom anode was developed for high-performance flexible perovskite LEDs (PeLEDs). The addition of 1-ethyl-3-methylimidazolium tetracyanoborate (EMIM TCB) IL initiates a depth-dependent rearrangement of the PEDOT and PSS moieties within the PEDOT:PSS film and improves its conductivity by orders of magnitude. Additionally, the IL increases the work function of the PEDOT:PSS layer, leading to a reduced barrier for hole injection. The fabricated flexible green PeLEDs exhibited pure green emission at 520 nm with a maximum external quantum efficiency (EQE) of 11.6% and maximum luminance of 25566.8 cd/m2. Remarkably, the device retained 85% of its initial luminance after 5000 bending cycles at a 5 mm bending radius.