Germanium Solar Cell Amorphous Silicon Passivation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current germanium solar cells face challenges in achieving efficient passivation and contacting, particularly due to the high absorption coefficient of germanium, which leads to surface recombination issues and requires specific processing conditions that are not well-suited for other materials like silicon nitride or amorphous semiconductors.
Innovation Solution
A method involving the deposition of a thin layer of amorphous silicon using plasma-enhanced chemical vapor deposition (PECVD) on the germanium surface, followed by the application of a patterned metal layer and a controlled diffusion step to form conductive contacts, optimizing the process for temperatures below 300°C to maintain desirable passivation properties and low contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a passivation layer is applied to reduce surface recombination, then surface passivation quality improves, but contact formation complexity increases
Solution Approach 1:
The germanium surface is pre-cleaned with a hydrogen plasma treatment before passivation layer deposition. This preliminary cleaning step removes contaminants and prepares the surface for optimal passivation, ensuring low surface recombination without requiring complex contact formation processes later
Solution Approach 2:
A thin amorphous silicon passivation layer is deposited as an intermediary between the germanium substrate and the metal contact. This intermediate layer enables both good surface passivation and acceptable contact properties by mediating the interaction between the germanium and contact metal
2Productivity
If germanium is used as substrate material, then energy conversion efficiency improves, but surface recombination losses increase
Solution Approach 1:
The high absorption coefficient of germanium, which causes light to be absorbed close to the surface and creates surface recombination issues, is countered by using a hydrogen plasma cleaning step that removes surface contaminants and creates a clean interface. This converts the potentially harmful surface condition into a beneficial clean surface that minimizes recombination losses while maintaining germanium's high efficiency properties
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 effectively reduces surface recombination, achieves low contact resistivity, and enhances the efficiency of germanium solar cells and thermophotovoltaic cells by improving the passivation and contacting processes while maintaining cost-effectiveness.
Implementation Method 1
depositing a layer of amorphous silicon on top of the germanium surface, preferably by plasma enhanced chemical vapor deposition
Implementation Method 2
depositing a patterned layer of metal on top of the layer of amorphous silicon, and 'firing through' or diffusion of the metal through the layer of amorphous silicon by applying a temperature step
Data Source
AI summary
A method is disclosed for passivating and contacting a surface of a germanium substrate. A passivation layer of amorphous silicon material is formed on the germanium surface. A contact layer of metal, e.g., aluminum, is then formed on the passivation layer. The structure is heated so that the germanium surface makes contact with the contact layer. The aluminum contact layer can be configured for use as a mirroring surface for the back surface of the device. Thus, a passivated germanium surface is disclosed, as well as a solar cell comprising such a structure.