Manipulating Ionic Behavior with Bifunctional Additives for Efficient Sky‐Blue Perovskite Light‐Emitting Diodes

Abstract

Perovskite Light-emitting diodes (PeLEDs) have emerged as a promising technique for future high-definition displays due to their outstanding electroluminescent characters. However, the development of blue PeLEDs toward practical applications is seriously hindered by their inferior performance, which mainly arises from the detrimental halide ionic behavior and thus severe nonradiative recombination in mixed-halide blue perovskite materials. Herein, efficient sky-blue PeLEDs featuring spectrally stable emission at 483 nm are realized by employing bifunctional passivators of Lewis-base benzoic acid anions and alkali metal cations to simultaneously passivate the under-coordinated lead atoms and suppress halide ion migration. A decent external quantum efficiency (EQE) of 16.58% and a maximum EQE of 18.65% are achieved, which is further boosted to 28.82% through the optical outcoupling enhancement. This work demonstrates unique insight into the generality and individuality of this category of benzoates and puts forward a feasible guidance in choosing appropriate additives for efficient perovskite materials.

Deep-Blue Perovskite Light-Emitting Diodes Realized by a Dynamic Interfacial Ion Exchange

“…Halide perovskite-based light-emitting diodes (PeLEDs) are considered promising candidates for the next generation of solid-state displays due to perovskite’s optoelectronic properties, such as tunable band gap, high photoluminescence quantum yield (PLQY), and excellent color purity. − The state-of-the-art external quantum efficiency (EQE) of green and red PeLEDs have, respectively, reached 28.1% and 25.8%, and that of sky-blue devices has reached 18.65%. − For PeLEDs to be successfully commercialized in displays, a highly efficient device emitting saturated blue color is essential. However, the efficiency of deep-blue emitting PeLEDs still lags behind.…”

High-Performance Pure Red Quasi-Two-Dimensional Perovskite Light-Emitting Diodes with Bifunctional Potassium Trifluoroacetate Additive

“…32 Similarly, in Figure 2c, the dominant peaks of I 3d 3/2 and I 3d 5/2 shift from 619.1 and 630.59 eV to the high binding energy of 619.17 and 630.67 eV after the KTFA modification, owing to the ionic bonding between K + and iodide ions. 30 Figure 2d shows that trifluoroacetate's (TFA's) C�O bond stretching vibration shifts from 1688 cm −1 to a lower wavenumber of 1677 cm −1 in the KTFA and PbI 2 mixture owing to the interaction between the C�O and Pb 2+ ions. 32 Moreover, the N−H stretching vibration peak of POEAI, located at 3468 cm −1 , shifts to 3430 cm −1 in the KTFA and POEAI mixture, which is attributed to the intermolecular interaction of hydrogen bonding between F atoms and N−H (Figure 2e).…”

“…We use triexponential decay functions to fit the TRPL curves. 30,34 The parameters extracted from the fitted curves are summarized in Table S2 (Supporting Information). τ 1 is the fast decay time constant, which is related to nonradiative recombination caused by defects, while τ 2 and τ 3 represent the slow decay time constant, which is associated with radiative recombination.…”

“…Figure a shows that the oxygen atoms in the carboxylate anion (OC–O−) functional group have obvious electronegativity, making TFA – an electron-donating Lewis base. Therefore, TFA – can coordinate with the unsaturated Pb 2+ ions and form hydrogen bonds with POEA + . , Meanwhile, K + can form ionic bonds with halide ions, inhibiting the migration of halide ions and the generation of halide vacancies Figure b depicts the inferred interactions between KTFA additive and Quasi-2D perovskite.…”

Trifunctional Trichloroacetic Acid Incorporated Mixed-Halide Perovskites for Spectrally Stable Blue Light-Emitting Diodes

“…Typically, there are two strategies to achieve blue perovskite emitters: Reducing the size of bulk perovskites to exciton Bohr radius − and introducing chloride into perovskites to expand their bandgaps. , Unfortunately, the low-dimensional perovskites are in a dilemma over how to improve the poor electronic properties induced by the excess large-size organic cations or ligands. − Meanwhile, the mixed chloride/bromide perovskites confront the challenges of low photoluminescence quantum yields (PLQYs) and poor spectra stability resulting from the chloride vacancy defects and resultant halide ion migration under electric field. ,− Therefore, it is critical to suppress the defect formation in perovskite films, including halide vacancy, uncoordinated Pb 2+ ions, etc. − For example, Karlsson et al demonstrated a vapor-assisted crystallization technique that can effectively suppress the ion migration in mixed-halide blue PeLEDs . Xu et al investigated the passivation effect of phosphine oxide additive in different antisolvents, in which PO groups could reduce the defect density effectively, thus resulting in an EQE of 9.5% at 488 nm .…”