Mixed Perovskite Formulation for Alpha Phase Formation
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Solution Overview
Problem
The formation of specific crystalline phases in hybrid organic-inorganic perovskite materials is challenging, particularly in thin films, due to phase transitions at low temperatures, leading to suboptimal electronic properties and contamination by unreacted starting materials, which affects the efficiency and stability of photovoltaic devices.
Innovation Solution
A formulation comprising specific ratios of cations and anions that form A′X′-containing compounds, which are ionically bonded and volatile, allowing for the preferential formation of the alpha phase with a band gap below 3.0 eV, using a one-step deposition process under ambient conditions, ensuring complete conversion of starting materials and minimal impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional perovskite formation methods are used, then material can be deposited, but the desired crystalline phase cannot be preferentially formed and phase transitions occur at low temperatures
Solution Approach 1:
The patent modifies the chemical composition parameters of the perovskite material by incorporating mixed cations (methylammonium and formamidinium) and mixed halides (iodide and bromide) in specific ratios. This compositional parameter change stabilizes the desired alpha-phase crystalline structure at lower temperatures and prevents phase transitions, thereby achieving preferential formation of the desired phase with improved electronic properties
Solution Approach 2:
The patent creates a composite perovskite material combining multiple cations (MA, FA) and halides (I, Br) to form a mixed organic-inorganic perovskite with formula MA1-xFAxPbI3-yBry. This composite approach leverages the complementary properties of different components: MA provides structural stability, FA extends light absorption, and Br incorporation stabilizes the alpha-phase, collectively achieving preferential crystalline phase formation
2Manufacturing precision
If complete conversion of starting materials is achieved, then impurities are minimized, but process conditions must be precisely controlled
Solution Approach 1:
The patent employs preliminary action by pre-mixing the cationic precursors (methylammonium iodide and formamidinium iodide) and halide precursors (lead iodide and lead bromide) in precisely calculated stoichiometric ratios before deposition. This pre-preparation ensures that during the deposition process, all starting materials can completely convert to the desired perovskite phase without leaving unreacted impurities, while simplifying process control
3Ease of manufacture
If ambient processing conditions are used, then cost and complexity are reduced, but phase purity and material quality may suffer
Solution Approach 1:
The patent utilizes parameter changes by exploiting the specific thermal stability characteristics of the mixed-cation mixed-halide perovskite composition. The incorporation of bromide and optimized cation ratios raises the phase transition temperature, allowing the material to maintain phase purity and crystalline structure during ambient processing conditions, thus achieving both ease of manufacture and high phase purity
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 achieves >90% formation of the desired crystalline phase with minimal impurities, enhancing the electronic properties and stability of perovskite films, suitable for photovoltaic applications, and allows for ambient processing, reducing costs and complexity.
Implementation Method 1
the one or more second cations A′ and the one or more second anions X′ are selected to form one or more A′X′-containing compounds which are able to be fully or substantially fully separated from the AMX3 material at a temperature which maintains the required crystalline structure of the hybrid perovskite material
Implementation Method 2
the one or more A′X′-containing compounds which are able to be fully or substantially fully separated from the AMX3 material at a temperature which maintains the required crystalline structure
Implementation Method 3
the amount of and choice of the one or more second cations A′ and one or more second anions X′ is selected to form one or more A′X′-containing compounds which are able to be fully or substantially fully separated from the AMX3 material at a temperature which maintains the required crystalline structure of the hybrid perovskite material
Data Source
AI summary
A formulation for use in the preferential formation of thin films of a perovskite material AMX3 with a certain required crystalline structure, wherein said formulation comprises two or more compounds which between them comprise one or more first organic cations A; one or more metal cations M; one or more second cations A′; one or more first anions X and one or more second anions X′.