TOPCon Solar Cell Poly-Silicon Crystallization via Hydrogen Plasma
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Solution Overview
Problem
In the large-scale production of N-type tunnel oxide passivating contact (TOPCon) solar cells, converting amorphous silicon into polycrystalline silicon during the annealing process is challenging, affecting field passivation and contact performance.
Innovation Solution
A method involving multiple cycle periods of depositing a target amorphous silicon layer and performing hydrogen gas plasma treatment improves the crystallization rate, with specific conditions such as flow rates and treatment times optimizing the conversion to polycrystalline silicon, enhancing field passivation and contact performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional PECVD or PVD methods are used to deposit amorphous silicon layer, then the production process is simple and efficient, but the crystallization rate of converting amorphous silicon into polycrystalline silicon is low
Solution Approach 1:
The patent applies preliminary action by performing hydrogen plasma treatment on the amorphous silicon layer before the annealing process. This pre-treatment introduces hydrogen atoms into the amorphous silicon structure, which act as nucleation sites for crystal formation during subsequent annealing, thereby significantly improving the crystallization rate without requiring complex equipment changes
Solution Approach 2:
The patent changes the physical-chemical parameters of the amorphous silicon layer by exposing it to hydrogen plasma. This treatment modifies the atomic structure and chemical composition of the layer, creating conditions that favor polycrystalline formation during annealing. The parameter change involves introducing hydrogen concentration and altering the atomic arrangement in the silicon layer
2Reliability
If amorphous silicon layer is deposited using conventional methods, then the field passivation performance is insufficient, but increasing the annealing temperature to improve crystallization may damage other cell structures
Solution Approach 1:
The patent uses hydrogen plasma as an intermediary substance to improve field passivation performance. The hydrogen atoms introduced during plasma treatment passivate dangling bonds and defects in the amorphous silicon layer, enhancing field passivation without requiring high annealing temperatures that could damage other cell structures
Solution Approach 2:
The patent changes the chemical composition parameter of the amorphous silicon layer by introducing hydrogen through plasma treatment. This compositional change improves the electrical properties and passivation characteristics of the layer, achieving better field passivation performance without increasing the annealing temperature
3Productivity
If multiple cycle periods of deposition and plasma treatment are implemented, then the crystallization rate improves, but the production time increases
Solution Approach 1:
The patent applies periodic action by implementing multiple cycles of thin amorphous silicon deposition followed by hydrogen plasma treatment. Each cycle builds upon the previous one, with the cumulative effect of hydrogen introduction and structural modification leading to significantly improved crystallization rate during the final annealing process
Solution Approach 2:
The patent segments the amorphous silicon layer formation into multiple thin layers deposited in separate cycles. Each layer undergoes plasma treatment individually, allowing controlled hydrogen incorporation. This segmentation enables better overall crystallization compared to depositing a single thick layer, as each thin layer can be optimally treated
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 method effectively improves the crystallization rate of amorphous silicon to polycrystalline silicon, leading to enhanced field passivation and contact performance, as well as increased open circuit voltage (Voc) and fill factor (FF) of the solar cell.
Implementation Method 1
performing a hydrogen gas plasma treatment on the target amorphous silicon preformed layer
Implementation Method 2
performing an annealing treatment on the target amorphous silicon layer to convert the target amorphous silicon layer into a target polycrystalline silicon layer
Implementation Method 3
hydrogen atoms can also easily enter an interface between a silicon wafer and a tunneling oxide layer, so that a large quantity of silicon suspension bonds at the interface can be saturated
Data Source
AI summary
In one aspect, a preparation method for a solar cell includes: forming a target amorphous silicon layer on a side of a silicon wafer using a preset process, and then performing an annealing treatment on the target amorphous silicon layer to convert the target amorphous silicon layer into a target polycrystalline silicon layer, wherein the preset process includes at least one cycle period, the at least one cycle period comprises: depositing a target amorphous silicon preformed layer with a preset thickness and performing a hydrogen gas plasma treatment on the target amorphous silicon preformed layer, wherein the preset thickness of the target amorphous silicon preformed layer is less than or equal to a thickness of the target amorphous silicon layer. This method can effectively improve a crystallization rate of converting amorphous silicon into polycrystalline silicon, improving field passivation performance and contact performance of the solar cell.