Perovskite Core-Shell Nanocrystals for Multiphoton Upconversion
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Solution Overview
Problem
Current materials struggle with achieving stable and efficient multiphoton excited upconversion photoluminescence and low-threshold upconversion lasing due to low transition probabilities in organic molecules and conventional inorganic semiconductors, and challenges in realizing multiphoton pumped lasing for applications like deep tissue imaging and optical communications.
Innovation Solution
Development of core-shell type organic-inorganic perovskite nanocrystals with a small organic cation core and a large organic cation shell, enhancing photoluminescence quantum yield and stability through dielectric confinement and surface passivation, and encapsulating these nanocrystals in a matrix for improved cytotoxicity reduction and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional inorganic semiconductors or organic molecules are used for multiphoton absorption, then the material structure is simple, but the transition probability is low resulting in poor photoluminescence quantum yield
Solution Approach 1:
The patent employs core-shell type organic-inorganic perovskite nanocrystals combining organic cations (methylammonium, formamidinium) with inorganic components (lead halides). This composite structure achieves high photoluminescence quantum yield (exceeding 80%) and large multiphoton absorption cross-sections, resolving the contradiction between simple material composition and high performance by creating a hybrid material system that leverages advantages of both organic and inorganic components
Solution Approach 2:
The nanocrystals are segmented into discrete quantum-confined structures with controlled sizes (3-10 nm diameter). This segmentation into nanoscale building blocks enables quantum confinement effects that enhance photoluminescence properties while maintaining colloidal stability and processability, achieving high reliability through size-controlled quantum effects
2Reliability
If perovskite nanocrystals are used for optical limiting applications, then the multiphoton absorption properties are enhanced, but the stability under ambient conditions deteriorates
Solution Approach 1:
The patent uses organic ligands (oleic acid, oleylamine) as intermediary molecules that passivate surface defects and stabilize the perovskite nanocrystal structure. These ligands form protective layers on the nanocrystal surface, preventing degradation from moisture and oxygen while maintaining the optical properties, thus resolving the contradiction between enhanced optical performance and ambient stability
Solution Approach 2:
The patent employs organic-inorganic hybrid shell structures that provide flexible protection to the perovskite core. The shell comprises perovskite nanocrystals coated with organic ligands forming a protective thin film layer, which maintains structural integrity and prevents degradation under ambient conditions while preserving the nonlinear optical properties for optical limiting applications
3Illumination intensity
If high incident light intensity is used to achieve multiphoton absorption, then the upconversion photoluminescence is enhanced, but the damage to biological tissues increases
Solution Approach 1:
The patent utilizes perovskite nanocrystals with exceptionally large multiphoton absorption cross-sections (one to two orders of magnitude larger than conventional semiconductors). This parameter change in absorption efficiency allows achieving the same upconversion photoluminescence intensity at much lower incident light intensities, thereby reducing photodamage to biological tissues while maintaining high imaging quality for deep tissue imaging applications
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 core-shell nanocrystals exhibit enhanced multiphoton absorption properties, leading to high photoluminescence quantum yield and stability, suitable for optical limiting, bioimaging, and upconversion lasing applications, with significantly improved performance in multiphoton excited processes.
Implementation Method 1
their large nonlinear optical properties (especially multiphoton absorption) of the perovskite NCs, which is essential for applications in optical-limiting, multiphoton microscopy for deep tissue imaging
Implementation Method 2
high photoluminescence quantum yield (PLQY)... colloidal nanocrystals (NCs) of organic-inorganic and all-inorganic halide perovskites have exhibited further improved light-emitting performance
Implementation Method 3
the colloidal nanocrystals (NCs) of organic-inorganic and all-inorganic halide perovskites have exhibited further improved light-emitting performance due to the quantum confinement effect, which results in increased PLQY, tunable optical bandgap and PL wavelength
Implementation Method 4
enhancing photoluminescence quantum yield and stability through dielectric confinement and surface passivation
Implementation Method 5
enhancing photoluminescence quantum yield and stability through dielectric confinement and surface passivation
Data Source
AI summary
Provided is a nanocrystal comprising a core comprised in a shell, wherein the core comprises a first material of a perovskite structure comprising a first organic cation not exceeding a molar weight of about 45 g/mol, a first divalent metal and a first counter anion, and, wherein the shell comprises a second material of a perovskite structure comprising a second organic cation having a molar weight between about 74 g/mol and about 187 g/mol, optionally the first organic cation, a second divalent metal and a second counter anion. Provided is further a matrix having the nanocrystal as defined above encapsulated therein. Provided is further a process for the synthesis of a nanocrystal comprising a core comprised in a shell, the process comprising a) preparing a precursor solution containing at least one divalent metal, a first organic cation not exceeding a molar weight of about 45 g/mol, a second organic cation having a molar weight between about 74 g/mol and about 187 g/mol, and at least one counter anion in a polar aprotic solvent; and b) subjecting the precursor solution to a non-polar solvent to form the nanocrystal.