Carbon-Dioxide-Graded Passivation for Heterojunction Solar Cells
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Solution Overview
Problem
The cost of silicon heterojunction solar cells is higher than that of PERC solar cells, necessitating a reduction in cost while maintaining or improving output power, which is linked to the cell-to-module (CTM) value.
Innovation Solution
A method for preparing heterojunction solar cells involves depositing a first passivation layer with a hydrogenated amorphous silicon using a gas source that gradually incorporates carbon dioxide, controlling the carbon dioxide proportion to increase with layer thickness, and employing a gradient concentration of doping atoms to enhance the CTM value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional heterojunction solar cell preparation methods are used, then good passivation effect and high open circuit voltage are achieved, but the CTM value and output power need further improvement
Solution Approach 1:
The patent applies local quality by creating a passivation layer with non-uniform doping concentration distribution. The doping concentration varies through the thickness of the layer, with different regions having different concentrations to optimize both passivation performance and electrical characteristics, thereby improving CTM value while maintaining good passivation effect.
Solution Approach 2:
The patent changes the doping concentration parameter through the thickness of the passivation layer. By gradually varying the doping concentration from the substrate interface toward the outer surface, the patent optimizes the balance between passivation quality and electrical performance, achieving improved CTM value without sacrificing passivation effectiveness.
2Reliability
If the first passivation layer thickness is increased to improve passivation effect, then open circuit voltage is maintained, but short-circuit current and fill factor are adversely affected
Solution Approach 1:
The patent uses local quality by implementing spatially varying doping concentration within the passivation layer. The region near the substrate interface has higher doping concentration to maintain open circuit voltage, while the outer regions have lower concentration to reduce recombination losses and improve short-circuit current and fill factor.
Solution Approach 2:
The patent introduces dynamic variation in doping concentration through the layer thickness. This gradual transition in material properties allows the passivation layer to simultaneously provide strong passivation for voltage maintenance and low recombination for current enhancement, resolving the trade-off between these parameters.
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 increases the CTM value and output power of heterojunction solar cells by optimizing the passivation layer structure, balancing short-circuit current and fill factor, thereby enhancing overall efficiency.
Implementation Method 1
depositing a first passivation layer on a first surface of a silicon substrate by using a gas source, during depositing hydrogenated amorphous silicon of the first passivation layer, allowing the gas source to gradually incorporate carbon dioxide
Data Source
AI summary
A preparation method of a heterojunction solar cell includes following steps: depositing a first passivation layer on a first surface of a silicon substrate by using a gas source, a base material of the first passivation layer being hydrogenated amorphous silicon; during depositing hydrogenated amorphous silicon of the first passivation layer, allowing the gas source to gradually incorporate carbon dioxide, and controlling a proportion of carbon dioxide in the gas source to gradually increase with increase of a thickness of the first passivation layer which has been deposited.