Highly Solvent Resistant Small-Molecule Hole-Transporting Materials for Efficient Perovskite Quantum Dot Light-Emitting Diodes

Abstract

Perovskite quantum dot light-emitting diodes (Pe-QLEDs) have been shown as promising candidates for nextgeneration displays and lightings due to their unique feature of wide color gamut and high color saturation. Hole-transporting materials (HTMs) play crucial roles in the device performance and stability of Pe-QLEDs. However, small-molecule HTMs have been less studied in Pe-QLEDs due to their poor solvent resistance and low hole mobility. In this work, three novel small-molecule HTMs employing benzimidazole as the center core, named X4, X5, and X6, were designed and synthesized for application in Pe-QLEDs. One of the tailored HTM-X6 exhibits excellent solvent resistant ability to the perovskite quantum dot (QD) inks due to its proper solubility and low surface energy. Our result clearly demonstrated that the synergistic effect of poor solubility and low surface energy facilitates the achievement of good solvent resistance to perovskite QD inks. As a result, a promising maximal external quantum efficiency (EQE) of 14.1% is achieved in X6-based CsPbBr 3 Pe-QLEDs, which is much higher than that of X4 (9.16%) and X5 (6.60%)-based devices, which is comparable to the PTAA reference (EQE ∼ 15.8%) under the same conditions. To the best of our knowledge, this is the first example that a benzimidazole-based small-molecule HTM demonstrated a good application in Pe-QLEDs. Our work provides new guidance for the rational design of small-molecule HTMs with high solvent resistance for efficient Pe-QLEDs and other photoelectronic devices.

Exploring Efficient Dual-Phase Emissive Fluorophores with High Mobility by Integrating a Rigid Donor and Flexible Acceptor

“…The molecular design strategy for excellent-performance luminophores has evolved from a single-molecule perspective to include an aggregate perspective. − However, achieving a high emission efficiency in both the single-molecule and aggregate states poses a significant challenge. Traditional organic luminogens with large π-conjugated fragments emit strongly when they lack significant intermolecular interactions, but serious fluorescence quenching occurs in the aggregate state. , One approach for exhibiting robust emission in aggregates involves the incorporation of aggregation-induced emission luminogens (AIEgens), while faint emission is demonstrated in a single-molecule state due to the quick intramolecular motion. − Another valid strategy is to enhance the intermolecular dipole–dipole interaction or electrostatic interaction in aggregates through preforming donor–acceptor (D–A) type geometry, which weakens the strong π–π stacking. − Simultaneously, such electrostatic interaction contributes to realizing dense and periodic packing, providing an effective conducting pathway and improving carrier mobility. − A single semiconductor with both high mobility and strong fluorescence emission is highly desired for the application in the organic optoelectronic field. Hence, a concise but more precise molecular design for achieving dual-phase (single molecule and aggregate) highly emissive and dual-functional (emissive and semiconducting) luminophores is attractive and practical.…”

Eliminating Chlorine Vacancies of Perovskite Nanocrystals Using Hydrazine Cations Enables Efficient Pure Blue Light-Emitting Diodes

“…Perovskite light-emitting diodes (LEDs), encompassing both perovskite thin-film LEDs and perovskite nanocrystal LEDs, are highly regarded as promising candidates for the next generation of displays due to their exceptional properties. These include solution processability, high defect tolerance, tunable bandgap, high photoluminescence quantum yield (PLQY), and vivid color saturation. − Remarkable strides have been made in the development of pure red and green perovskite-based LEDs, achieving efficiencies surpassing 20%. − However, the efficiency of blue LEDs, especially those aiming for a pure blue LED toward display devices, lags significantly behind their red and green counterparts. Currently, sky blue light (∼490 nm) perovskite LEDs have been reported with efficiencies exceeding 15%. , Nevertheless, as the wavelength decreases toward pure blue, ranging between 465 and 475 nm, a notable decline in device efficiency is observed. − The primary challenges faced by pure blue perovskite LEDs are low efficiency, short lifetime, and poor spectral stability.…”