Polycrystalline Silicon Solar Cell Vertical Crystallization
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Solution Overview
Problem
Current solar cell technologies face challenges in achieving high efficiency due to metal contamination and random grain growth in polycrystalline silicon thin films, leading to increased recombination of electrons and holes, which decreases solar cell efficiency and stability.
Innovation Solution
A method involving metal-induced lateral crystallization (MILC) and metal-induced vertical crystallization (MIVC) processes is used to form a light-absorbing layer of non-polluted polycrystalline silicon, where grains are vertically grown to minimize grain boundaries, reducing metal contamination and enhancing solar cell efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If metal-induced crystallization (MIC) is used to form polycrystalline silicon light-absorbing layer, then crystallization can be achieved at low temperature, but metal contamination occurs leading to increased recombination of electrons and holes
Solution Approach 1:
The patent extracts and removes the harmful metal catalyst from the system after it has served its purpose. The metal-induced crystallization is performed to convert amorphous silicon to polycrystalline silicon at low temperature, then the metal catalyst is removed through selective etching or other separation techniques, leaving clean polycrystalline silicon without metal contamination that would cause carrier recombination.
Solution Approach 2:
The patent uses a metal catalyst as an intermediary substance that facilitates the crystallization process temporarily. The metal is introduced to induce crystallization of amorphous silicon at low temperature, performs its mediating function, and is then removed. This allows the beneficial low-temperature crystallization while eliminating the harmful residual metal contamination.
2Ease of manufacture
If conventional polycrystalline silicon structure is used, then manufacturing is simpler, but random grain growth increases grain boundaries acting as recombination sites
Solution Approach 1:
The patent applies local quality by creating a specific vertical columnar grain structure where grains grow perpendicular to the substrate surface. This localized directional growth pattern, rather than random grain orientation, reduces the number of grain boundaries in the path of charge carriers. The uniform vertical alignment throughout the light-absorbing layer minimizes recombination sites while maintaining manufacturability through controlled crystallization processes.
3Strength
If wafer-type silicon solar cell with thickness of 300-400 μm is used, then mechanical strength is sufficient, but production cost increases and cutting damage occurs
Solution Approach 1:
The patent changes the fundamental parameter of silicon layer thickness from conventional 300-400 μm to a thin film structure. By using amorphous silicon that is crystallized in-situ, the mechanical strength requirement is redefined - the thin film is supported by the substrate and the crystallization process itself provides structural integrity. This parameter change enables reduced material usage and cost while avoiding cutting damage entirely, as the silicon is deposited and crystallized in its final thin form rather than being cut from thick wafers.
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 results in a high-efficiency polycrystalline silicon solar cell with reduced recombination frequency of electrons and holes, improving solar cell performance and stability by minimizing grain boundaries and metal contamination.
Implementation Method 1
the light-absorbing layer is formed of non-polluted polycrystalline silicon using a metal-induced lateral crystallization (MILC) process
Implementation Method 2
grains of the polycrystalline silicon are vertically grown in the direction in which electrons and holes move using a metal-induced vertical crystallization (MIVC) process
Implementation Method 3
Solar photovoltaic power generation, which is a technology of directly converting solar energy into electric energy using a photovoltaic effect
Data Source
AI summary
Disclosed herein is a method of forming a light-absorbing layer of a polycrystalline silicon solar cell, including: forming a polycrystalline silicon layer on a back electrode; forming an intrinsic amorphous silicon layer on the polycrystalline silicon layer; and heat-treating the transparent insulating substrate to vertically crystallize the intrinsic amorphous silicon layer using the polycrystalline silicon layer as a seed for crystallization through a metal induced vertical crystallization (MIVC) process to form the intrinsic amorphous silicon layer into a light-absorbing layer made of polycrystalline silicon, and is a method of fabricating a high-efficiency polycrystalline silicon solar cell using the light-absorbing layer.