Wide-Bandgap Emitter Passivation for Silicon Solar Cells
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Solution Overview
Problem
Current solar cell manufacturing processes face inefficiencies due to complex handling and high costs associated with multiple process operations for surface passivation and dielectric formation, which can lead to exposure to contaminants and reduced solar cell efficiency.
Innovation Solution
A method involving the formation of a thin dielectric layer and a deposited wide bandgap semiconductor layer on a silicon substrate in a single process tool, using techniques like low-pressure chemical vapor deposition and rapid thermal anneal, to create a single-operation passivation process that prevents atmospheric exposure and simplifies the fabrication sequence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple process operations are used for surface passivation and dielectric formation, then comprehensive protection and functionality are achieved, but processing complexity and cost increase
Solution Approach 1:
The patent combines surface passivation and dielectric formation into a single integrated process step, where a dielectric layer with embedded passivation functionality is deposited in one operation. This merging eliminates the need for separate passivation and dielectric formation steps, reducing processing complexity while maintaining comprehensive protection and functionality.
Solution Approach 2:
The dielectric layer is designed to perform multiple functions simultaneously: it provides electrical isolation, mechanical protection, and surface passivation. By incorporating passivation functionality directly into the dielectric layer structure, the material serves universal purposes that would traditionally require separate specialized layers or processes.
2Reliability
If multiple process operations are performed, then thorough surface treatment is achieved, but exposure to contaminants increases
Solution Approach 1:
By combining surface passivation and dielectric formation into a single continuous process step, the substrate surface remains under controlled process conditions throughout. The surface is not exposed to atmospheric contaminants between separate operations, as the entire process completes in one controlled environment without intermediate exposures.
Solution Approach 2:
The passivation functionality is incorporated into the dielectric layer during its formation process, rather than requiring subsequent separate passivation steps. This preliminary integration ensures the surface is protected and passivated during the very formation of the dielectric layer, preventing contaminant exposure that would occur with sequential operations.
3Reliability
If conventional separate processes are used for passivation and dielectric formation, then each function is optimized, but manufacturing efficiency decreases
Solution Approach 1:
The patent merges surface passivation and dielectric formation into a single process operation, eliminating the need for multiple sequential steps. This integration directly increases manufacturing efficiency by reducing the total number of process steps, cycle time, and handling operations while maintaining the quality benefits of both functions.
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 enhances solar cell efficiency by providing superior passivation and ohmic contact while reducing processing complexity and costs, enabling full-area metal contact formation and improved optical reflectance without the need for additional processing steps.
Implementation Method 1
low-pressure chemical vapor deposition
Implementation Method 2
rapid thermal anneal
Implementation Method 3
Solar radiation impinging on the surface of, and entering into, the substrate creates electron and hole pairs in the bulk of the substrate
Data Source
AI summary
Solar cells having emitter regions composed of wide bandgap semiconductor material are described. In an example, a method includes forming, in a process tool having a controlled atmosphere, a thin dielectric layer on a surface of a semiconductor substrate of the solar cell. The semiconductor substrate has a bandgap. Without removing the semiconductor substrate from the controlled atmosphere of the process tool, a semiconductor layer is formed on the thin dielectric layer. The semiconductor layer has a bandgap at least approximately 0.2 electron Volts (eV) above the bandgap of the semiconductor substrate.