Multifunctional Conjugated Molecular Additives for Highly Efficient Perovskite Light-Emitting Diodes.

Area of Science:

• Materials Science
• Optoelectronics
• Solid-State Physics

Background:

• Perovskite light-emitting diodes (PeLEDs) face challenges in optimization due to crystal deformation, residual stress, and defect-induced non-radiative recombination.
• Existing molecular additives for defect passivation often possess insulating properties, hindering crucial charge injection and transport processes.

Purpose of the Study:

• To develop highly efficient green-emitting PeLEDs by introducing novel semiconducting molecular additives.
• To investigate the impact of these additives on perovskite crystal quality, charge transport, and device performance.

Main Methods:

• Synthesis and incorporation of semiconducting molecular additives (Fl-OEGA and Fl-C8A) into 3D CsPbBr3-PeLEDs.
• Characterization using Transmission Electron Microscopy (TEM) and Kelvin Probe Force Microscopy (KPFM).
• Analysis of residual stress, ion migration activation energy, and device electrical properties.

Main Results:

• Conjugated semiconducting additives were observed at perovskite grain boundaries, reducing contact potential difference variations.
• A 13% reduction in residual tensile stress and increased ion migration activation energy were achieved with Fl-OEGA.
• Semiconducting additives maintained charge transport capability, unlike insulating additives, leading to negligible turn-on voltage shifts and smaller current density decreases.

Conclusions:

• Semiconducting molecular additives, specifically Fl-OEGA, serve as effective multifunctional additives for high-performance PeLEDs.
• These additives mitigate detrimental effects of stress and defects while preserving efficient charge transport.
• The optimized 3D CsPbBr3-PeLEDs achieved a record external quantum efficiency of 21.3%.