Stable Energy-Level Regulation of NiO_x for Efficient Deep-Blue Perovskite LEDs

Area of Science:

• Materials Science
• Optoelectronics
• Chemistry

Background:

• Nickel oxide (NiO_x) is a promising hole injection layer for perovskite light-emitting diodes (PeLEDs) due to its tunable energy levels via molecular modification.
• Conventional modifiers often detach during perovskite deposition, leading to energy level instability and reduced device performance.

Purpose of the Study:

• To develop a stable interfacial molecular modification strategy for NiO_x to enhance PeLED performance.
• To investigate the effect of multidentate anchoring on modifier adsorption stability and energy-level alignment.

Main Methods:

• Employed a multidentate anchoring strategy using 4-bromophenylphosphonic acid (BPA) to improve modifier adsorption on NiO_x.
• Investigated the adsorption strength and surface coverage of BPA on NiO_x using experimental methods.
• Fabricated deep-blue PeLEDs using the modified NiO_x and pure-halide quasi-2D perovskites.

Main Results:

• The multidentate anchor (BPA) achieved high adsorption strength (-6.47 eV) and >95% surface coverage after solvent rinsing.
• The modified NiO_x exhibited favorable energy-level alignment with a small barrier (<0.69 eV).
• The fabricated PeLEDs showed a champion external quantum efficiency (EQE) of 15.8% at 463 nm and a record-low turn-on voltage of 2.4 V.

Conclusions:

• Multidentate anchoring effectively enhances the stability of molecular modifiers on NiO_x, preventing energy-level shifts.
• This strategy leads to improved charge injection and transport in PeLEDs, enabling high-efficiency deep-blue emission.
• The approach is scalable for large-area PeLED fabrication, demonstrating a pathway towards practical applications.