Multifunctional Conjugated Molecular Additives for Highly Efficient Perovskite Light‐Emitting Diodes

Abstract

Further optimization of perovskite light‐emitting diodes (PeLEDs) is impeded by crystal deformation caused by residual stress and defect formation with subsequent non‐radiative recombination. Molecular additives for defect passivation are widely studied; however, the majority have insulating properties that hinder charge injection and transport. Herein, highly efficient green‐emitting PeLEDs are reported by introducing semiconducting molecular additives (Fl‐OEGA and Fl‐C8A). Transmission electron microscopy shows that conjugated additives exist primarily at the grain boundaries of perovskite, and Kelvin probe force microscopy confirms that the variation in contact potential difference between grain boundaries and perovskite crystal domains is significantly reduced. The residual tensile stress is reduced by 13% and the activation energy for ion migration increases in the Fl‐OEGA‐treated perovskite film, compared to those of the film without additives. Compared to insulating 2,2′‐(ethylenedioxy)diethylamine (EDEA), the introduction of semiconducting additives prevents a significant reduction in the charge‐transport capability. Furthermore, the PeLEDs with Fl‐OEGA show a negligible shift in the turn‐on voltage and a significantly smaller decrease in the current density with increasing Fl‐OEGA compared to the devices with EDEA. Finally, the 3D CsPbBr3–PeLEDs show the highest external quantum efficiency of 21.3% by the incorporation of semiconducting Fl‐OEGA as a new multifunctional additive.

Hydrogen Bond-Assisted Dual Passivation for Blue Perovskite Light-Emitting Diodes

“…Computational details can be found in the experimental section. As the theoretical analysis presented above, we speculate that the coordination of DPPA and the quasi-2D perovskites occurs predominantly between the PO group and the unsaturated Pb 2+ ions, where Lewis base-acid interactions effectively mitigate perovskite defects. − Meanwhile, the active hydrogen atoms of the -NH 2 group form hydrogen bonds with adjacent halide ions, which further strengthen the passivation effect of DPPA on the perovskite.…”

Anionic Conjugated Polyelectrolyte as a Semiconducting Additive for Efficient and Stable Perovskite Solar Cells

“…Given that defects in MHPs bear either positive or negative charges, a range of passivating materials possessing corresponding charges have been introduced into PSCs. 8,14,15 These passivation endeavors generally adopt one of three approaches: top-down passivation, bottom-up passivation, and additives. While interfacial passivation strategies (top-down and bottomup) offer the advantage of energy level alignment, their passivation effectiveness tends to remain confined to the surface, with limited penetration into inner grain bounda- ries.…”

“…Diverse strategies have been extensively explored to elevate the performance of PSCs through effective defect passivation. Given that defects in MHPs bear either positive or negative charges, a range of passivating materials possessing corresponding charges have been introduced into PSCs. ,, These passivation endeavors generally adopt one of three approaches: top-down passivation, bottom-up passivation, and additives. While interfacial passivation strategies (top-down and bottom-up) offer the advantage of energy level alignment, their passivation effectiveness tends to remain confined to the surface, with limited penetration into inner grain boundaries. , To comprehensively address this challenge, the introduction of passivating materials as additives in the MHP precursor stage has emerged as a potent alternative.…”

Self-Stabilized Quasi-2D Perovskite with an Ion-Migration-Inhibition Ligand for Pure Green LEDs

“…Passivating the halide vacancy defects is a commonly adopted strategy to improve the performance and stability of quasi-2D PeLEDs, ,,− especially incorporating exogenous passivation additives into the perovskite films to inhibit ion migration . Different types of organic chemicals, including small molecules and polymers with Lewis base groups, such as PO, CO, SO, and C–O–C, have been employed as the additives. − However, some associated structures of alkyl or other low-conductive structures are inevitably brought in simultaneously, which hinders the carrier transport in perovskite films. ,− Exogenous additives with better conductivity, such as conjugated molecules, have also been studied, , but it is still difficult to match their conductivity with the high conductivity of perovskites. Recently, as a necessary component in the quasi-2D perovskite, organic spacer ligands have been further designed to be equipped with functional groups.…”