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Solvent sieving technique extends lifespan of PeLEDs

Researchers from the Chinese Academy of Sciences (CAS) have used a simple solvent sieve method to develop efficient and stable perovskite light-emitting diodes (PeLEDs). Perovskites are a promising optoelectronic material due to their excellent optoelectronic performance and low preparation cost. Compared with traditional organic light-emitting diodes (OLEDs), PeLEDs have a narrower light-emitting spectrum and enhanced colour purity, thus showing great potential in display and lighting.

However, despite significant progress in efficiency, low operational stability has hindered the practical application of PeLEDs. A limited understanding of the cause of perovskite instability has also limited the development and commercialisation of PeLEDs. Following an in-depth analysis of the nanostructures of perovskites, the researchers identified the perovskites’ defective low n-phase as the key source of perovskite instability. The low quality of the low n-phase, which contained one or two layers of lead ions, originated from the rapid and uncontrollable crystallisation process.

Inspired by the process of separating sand of different sizes with a sieve, the researchers used a solvent sieve method to screen out the undesirable low n-phases. The solvent sieve is a combination of polar and nonpolar solvents. The polar solvent acts as a mesh that interacts with perovskites, while the nonpolar solvent acts as a framework that does not affect perovskites. The researchers adjusted the ratio of polar solvents to effectively remove the defective low n-phases.

The PeLEDs based on the sieved perovskites had an operating lifetime of more than 5.7 years under normal conditions (luminance of 100 cd/m2); this lifetime is reportedly the highest value recorded to date for green PeLEDs, reaching the fundamental threshold for commercial application. The PeLEDs also achieved a record high external quantum efficiency (EQE) of 29.5%, thereby improving the efficiency of converting electricity to light. When exposed to ambient air (50±10% humidity), the device can maintain 75% of its film photoluminescence quantum yield and 80% of its EQEE for more than 100 days, thus showing excellent stability.

The solvent sieve method improves the luminescence performance and stability of PeLEDs, but also paves the way for the development and application of perovskites with unique nanostructures and enhanced luminescence performance. The research findings were published in Nature Photonics.

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