Selective Emitter Solar Cell Doping With Preserved Passivation
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Solution Overview
Problem
The existing process for forming a selective emitter in solar cells is difficult to control, 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, an amorphous silicon layer, and a doped polycrystalline silicon layer through diffusion doping and laser doping, with specific temperature and thickness parameters, to create a selectively doped region that protects the passivation structure and reduces parasitic absorption.
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, then a selectively doped region can be 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 segments the silicon layer into three distinct parts: a first silicon layer with light doping, a second silicon layer with heavy doping, and a third silicon layer with intermediate doping. This segmentation allows each layer to serve a specific function - the first layer provides passivation, the second layer provides selective contact, and the third layer provides a transition zone, thereby preventing exposure of the silicon substrate while achieving selective emitter functionality.
Solution Approach 2:
The patent applies local quality by creating regions with different doping concentrations at different locations. The first silicon layer has light doping for passivation, the second silicon layer has heavy doping for contact, and the third silicon layer has intermediate doping for transition. This local differentiation of doping quality enables precise control over the selective emitter process while maintaining passivation structure integrity.
2Ease of manufacture
If the second silicon layer is removed to create selective emitter regions, then contact resistance is reduced, but the process is difficult to control and may remove the first silicon layer
Solution Approach 1:
The patent performs preliminary action by depositing the third silicon layer with intermediate doping between the first and second silicon layers. This intermediate layer is formed in advance to provide a buffer zone that prevents complete removal of the first silicon layer during subsequent processing, thereby facilitating selective emitter formation while maintaining process control.
Solution Approach 2:
The patent utilizes parameter changes by varying the doping concentration across three distinct silicon layers. The first layer has low doping concentration, the second layer has high doping concentration, and the third layer has intermediate doping concentration. This parameter differentiation enables controlled removal of the second layer while preserving the first layer, improving both ease of manufacture and process precision.
3Reliability
If heavy doping is applied at contact positions, then contact resistance is reduced, but parasitic absorption increases
Solution Approach 1:
The patent applies local quality by concentrating heavy doping in the second silicon layer only at the contact positions where metallization is applied. The first silicon layer maintains light doping to minimize parasitic absorption in non-contact areas. This localized differentiation of doping quality reduces contact resistance at electrode interfaces while minimizing parasitic absorption in the bulk of the silicon layer.
Solution Approach 2:
The patent segments the doped regions into distinct layers with different doping concentrations. The second silicon layer with heavy doping is confined to specific contact positions, while the first and third silicon layers with lighter doping cover the remaining areas. This segmentation isolates the heavy doping to where it is most beneficial for contact resistance, thereby reducing overall parasitic absorption.
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 improves the control of the selective emitter process, reduces parasitic absorption, and enhances the short-circuit current of the solar cell by maintaining the passivation structure and optimizing doping concentrations.
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, so that a doped polycrystalline silicon layer is formed on 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
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 at a first side; forming a doped polycrystalline silicon layer in a first process by a diffusion doping treatment; forming a doped oxide layer on the doped polycrystalline silicon layer in a second process; and after the doped oxide layer 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.