Selective Emitter Solar Cell with Laser Doping and Passivation Protection
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Solution Overview
Problem
Existing methods for preparing solar cells with selective emitter structures face challenges in controlling the process window, leading to the removal of the silicon layer and exposure of the silicon substrate, which results in the loss of the passivation structure on the back side.
Innovation Solution
A method involving the formation of a tunneling oxide layer, followed by an amorphous silicon layer, diffusion doping treatment to create a doped polycrystalline silicon layer and a doped oxide layer, and laser doping to form a heavily doped region, which includes specific temperature and thickness parameters to control the process and protect the tunneling oxide layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a second silicon layer with heavy doping is deposited on a first silicon layer with light doping and then removed according to metallization pattern, then selective emitter structure is formed, but it is difficult to control the process window and the first silicon layer is easily removed, exposing the silicon substrate and losing the passivation structure
Solution Approach 1:
The patent introduces a silicon nitride layer as an intermediary protective layer between the tunneling oxide layer and the doped polycrystalline silicon layer. This intermediary layer prevents direct contact and potential damage to the tunneling oxide layer during subsequent processing steps, thereby protecting the passivation structure while allowing selective emitter formation.
Solution Approach 2:
The patent performs preliminary actions by forming the tunneling oxide layer and silicon nitride layer before depositing and processing the doped polycrystalline silicon layer. This preliminary protection structure is established in advance to prevent potential damage during the selective emitter formation process.
2Productivity
If the thickness of the doped polycrystalline silicon layer is reduced, then parasitic absorption is minimized and short-circuit current is improved, but the passivation effect may be compromised
Solution Approach 1:
The silicon nitride layer serves as an intermediary that maintains passivation effectiveness even when the doped polycrystalline silicon layer is thinned. This protective layer ensures that the passivation function is not compromised by the reduced thickness of the silicon layer, allowing optimization for higher short-circuit current.
Solution Approach 2:
The patent uses a composite structure combining tunneling oxide layer, silicon nitride layer, and doped polycrystalline silicon layer. This composite material approach allows each layer to perform its specific function - the thin doped silicon layer minimizes parasitic absorption while the silicon nitride and tunneling oxide layers maintain passivation effectiveness.
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 method effectively reduces the thickness of the doped polycrystalline silicon layer, minimizing parasitic absorption and improving the short-circuit current of the solar cell while maintaining passivation, with a simpler process that is suitable for mass production.
Implementation Method 1
a layer of a tunneling oxide layer on a back side
Implementation Method 2
performing a diffusion doping treatment on the amorphous silicon layer, the diffusion doping treatment includes: a first process of introducing a doping source and an oxygen source into a diffusion chamber, and heating the amorphous silicon layer
Implementation Method 3
forming a heavily doped region on the doped polycrystalline silicon layer by a laser doping process
Data Source
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AI summary
A solar cell and a preparation method thereof are provided. A method for preparing the solar cell includes following steps: forming an amorphous silicon layer on a tunneling oxide layer (120) at a first side; forming a doped polycrystalline silicon layer (130) in a first process by a diffusion doping treatment; forming a doped oxide layer (131) on the doped polycrystalline silicon layer in a second process; and after the doped oxide layer (131) is formed, doping the first side selectively and heavily by a laser doping process, and forming a selective emitter region in a heavily doped region.