BaF2 Passivation in Porous Templates for Stable Perovskite Quantum Dots
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Solution Overview
Problem
Lead halide perovskite nanocrystals are prone to structural damage in high temperature and light exposure due to their ionic nature and soft lattice characteristics, leading to decreased luminescent performance and surface defects that reduce fluorescence intensity.
Innovation Solution
A fluorine-containing passivation layer, comprising BaF2, is formed on the surface of perovskite nanocrystals within an incompletely closed microporous/mesoporous template, using a hydrothermal reaction to enrich F ions and form a dense fluoride film that passivates surface defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If lead halide perovskite nanocrystals are used, then high fluorescence quantum yield and narrow full width at half maximum are achieved, but structural damage occurs in high temperature and humidity environments leading to decreased luminescent performance
Solution Approach 1:
The patent forms a composite structure by combining perovskite nanocrystals with a fluorine-containing passivation layer (comprising BaF2 and other metal fluorides). This composite material approach allows the perovskite core to maintain its high fluorescence quantum yield while the fluorine-containing shell provides structural stability and protection against environmental damage, particularly at temperatures above 70°C where lead hydroxide coatings fail.
Solution Approach 2:
The patent applies local quality modification by forming a fluorine-containing passivation layer specifically on the surface of the perovskite nanocrystals. This surface treatment locally enhances the chemical stability and structural integrity of the nanocrystal interface, protecting against environmental factors without affecting the bulk perovskite material's optical properties.
2Reliability
If coating materials such as mesoporous silica are used to encapsulate perovskite nanocrystals, then stability is enhanced, but surface defects remain resulting in decreased fluorescence intensity
Solution Approach 1:
The patent utilizes porous metal fluorides (comprising BaF2 and other metal fluorides) as the passivation layer material. These fluorine-containing porous materials can effectively penetrate and passivate surface defects on the perovskite nanocrystal surface, providing both stability enhancement and maintenance of high fluorescence intensity by eliminating surface defect-related non-radiative recombination.
Solution Approach 2:
The patent changes the chemical composition parameter of the passivation layer from conventional materials (like mesoporous silica) to fluorine-containing compounds. This parameter change enables the passivation layer to effectively bind with surface defects on the perovskite nanocrystals, converting harmful surface states into benign or beneficial sites, thereby maintaining fluorescence intensity while providing stability.
3Object-affected harmful factors
If lead hydroxide coating is formed on perovskite nanocrystals, then water and oxygen barrier properties are provided, but chemical stability decreases at temperatures above 70 degrees Celsius leading to passivation layer destruction
Solution Approach 1:
The patent changes the temperature stability parameter of the passivation layer by replacing lead hydroxide coating with a fluorine-containing passivation layer (comprising BaF2 and other metal fluorides). This parameter change results in a passivation layer that maintains chemical stability at temperatures above 70°C, eliminating the thermal decomposition issue while preserving the water and oxygen barrier properties needed for protecting perovskite nanocrystals.
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
The fluorine-containing passivation layer enhances the stability and luminescent performance of perovskite nanocrystals by reducing surface defects and maintaining luminescence intensity under high temperature and light exposure.
Implementation Method 1
introducing F ions into the pores of the microporous/mesoporous template to enrich the F ions within the pores
Implementation Method 2
soaking the microporous/mesoporous template grown with the perovskite nanocrystals containing barium in water to form a lead hydroxide coating on the surface of the perovskite nanocrystals containing barium; the lead hydroxide coating blocks contact between the F ions and the perovskite nanocrystals containing barium
Implementation Method 3
placing the microporous/mesoporous template containing the perovskite nanocrystals with barium, the lead hydroxide coating, and the enriched F ions under a hydrothermal reaction condition; during the hydrothermal reaction, the lead hydroxide coating disappears and a fluorine-containing passivation layer is formed on the surface of the perovskite nanocrystals
Data Source
AI summary
The present disclosure provides a method for constructing a fluorine-containing passivation layer for perovskite quantum dots, and the fluorine-containing passivation layer comprising a microporous/mesoporous template with incompletely closed pores, within which perovskite nanocrystals and a fluorine-containing passivation layer are grown. The fluorine-containing passivation layer is used to passivate surface defects of the perovskite nanocrystals; the fluorine-containing passivation layer includes BaF2. The present disclosure allows for the passivation of the surface of perovskite nanocrystals to improve stability without collapsing the microporous/mesoporous template.