Perovskite Nanocrystal Surface Passivation for Lower Recombination Loss
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Solution Overview
Problem
Hybrid organic-inorganic metal halide perovskite light emitting diodes (PeLEDs) suffer from non-radiative recombination mechanisms, which degrade external quantum efficiencies (EQEs) due to uncoordinated and undercoordinated surface sites on metal and halide elements, leading to reduced device performance compared to organic LEDs (OLEDs) and quantum dot LEDs (QLEDs).
Innovation Solution
The use of organic-inorganic perovskite nanocrystals with engineered surfaces, featuring growth passivation ligands larger than trap passivation ligands, which are unable to incorporate into octahedral corner sites, and trap passivation ligands that fill uncoordinated surface sites, reducing non-radiative recombination and enhancing device efficiencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional perovskite structures are used, then high carrier mobility is achieved, but non-radiative recombination mechanisms degrade external quantum efficiencies
Solution Approach 1:
The patent applies local quality by introducing two distinct types of passivation ligands with different functions: growth passivation ligands (larger molecules like oleic acid and oleylamine) that control nanocrystal formation and prevent incorporation into octahedral sites, and trap passivation ligands (smaller molecules like methylammonium iodide) that specifically fill uncoordinated surface sites. This differentiated local treatment of surface sites reduces non-radiative recombination while maintaining the overall perovskite structure and high carrier mobility.
Solution Approach 2:
The patent uses passivation ligands as intermediary substances that mediate between the perovskite crystal structure and the environment. These ligands bind to surface metal and halide sites, creating a protective interface that prevents harmful interactions while allowing the underlying perovskite to maintain its optoelectronic properties. The ligands act as intermediaries that fill surface vacancies and passivate trap states without disrupting the bulk crystal structure.
2Loss of energy
If trap passivation ligands fill uncoordinated surface sites, then non-radiative recombination is reduced, but device complexity increases due to multi-component surface engineering
Solution Approach 1:
The patent applies preliminary action by incorporating both growth passivation ligands and trap passivation ligands into the precursor solution before nanocrystal formation. The growth passivation ligands are already present during crystallization to control surface formation, and the trap passivation ligands are added in stoichiometric excess to ensure complete filling of surface sites. This pre-planned, multi-stage passivation approach simplifies the overall process compared to sequential treatment methods.
Solution Approach 2:
The patent achieves universality by using a combination of ligands that perform multiple functions simultaneously: growth passivation ligands control crystal formation and morphology while also providing initial surface coverage, and trap passivation ligands fill remaining vacancies. This multi-functional ligand system addresses multiple surface issues (uncoordinated sites, undercoordinated sites, morphology control) in a single integrated approach, reducing the need for separate processing steps.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach increases the external quantum efficiency of PeLEDs to above 15% by minimizing trap-assisted non-radiative recombination and promoting radiative recombination, resulting in improved performance and efficiency of optoelectronic devices.
Implementation Method 1
the trap passivation ligands fill uncoordinated and/or undercoordinated surface sites on metal and/or halide elements of the organic-inorganic perovskite nanocrystals
Implementation Method 2
the growth passivation ligands are larger than the trap passivation ligands and are of size unable to incorporate into octahedral corner sites of the perovskite crystal structure
Implementation Method 3
This approach increases the external quantum efficiency of PeLEDs to above 15% by minimizing trap-assisted non-radiative recombination and promoting radiative recombination
Data Source
AI summary
In one aspect, organic-inorganic nanoparticle compositions are described herein comprising engineered surfaces which, in some embodiments, reduce non-radiative recombination mechanisms, thereby providing optoelectronic devices with enhanced efficiencies. In some embodiments, a nanoparticle composition comprises a layer of organic-inorganic perovskite nanocrystals, the organic-inorganic perovskite nanocrystals comprising surfaces associated with growth passivation ligands and trap passivation ligands, wherein the growth passivation ligands are larger than the trap passivation ligands and are of size unable to incorporate into octahedral corner sites of the perovskite crystal structure.