Partial Tunnel Oxide Contact Structure for Low-Recombination Solar Cells
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Solution Overview
Problem
The excessive recombination current at the surface contact region between metallic electrodes and crystalline silicon in photovoltaic cells limits the further improvement of open circuit voltage and conversion efficiency, as existing tunnel oxide passivated contact structures are not compatible with front surface applications due to strong sunlight absorption by silicon-based films.
Innovation Solution
A partial tunnel oxide passivated contact structure for photovoltaic cells, where a first tunnel oxide layer and polysilicon film are specifically disposed only in the region for passivated contact, avoiding the light absorption region, and optionally a second tunnel oxide and polysilicon layer are used between the first layer and the cell body to enhance passivation and prevent damage from metallic electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tunnel oxide passivated contact is applied to suppress recombination at metallic contact region, then recombination is suppressed, but silicon-based film has strong absorption on sunlight which restricts application on front surface
Solution Approach 1:
The front surface is segmented into two distinct regions: a first region for light absorption and a second region for passivated contact. The tunnel oxide layer and polysilicon film are selectively applied only to the second region, allowing simultaneous optimization of both light absorption and recombination suppression without mutual interference.
Solution Approach 2:
Different functional regions are assigned different material configurations: the first region maintains silicon surface for optimal light absorption, while the second region receives tunnel oxide and polysilicon layers for recombination suppression. This local differentiation resolves the contradiction by applying passivation only where needed for contact regions.
2Reliability
If surface passivation is maximized to reduce recombination current, then open circuit voltage improves, but manufacturing complexity increases
Solution Approach 1:
A preliminary tunnel oxide layer is formed on the silicon surface before metal electrode deposition. This preliminary passivation layer is then selectively removed from the first region (light absorption area) while retained in the second region (contact area), enabling subsequent selective polysilicon film application. This preliminary action simplifies the overall process by establishing a foundation for selective passivation.
Solution Approach 2:
The tunnel oxide layer serves as an intermediary layer between the silicon surface and the metal electrode. It provides initial passivation and serves as a foundation for selective polysilicon film application, mediating between the silicon substrate and the metal contact while enabling controlled passivation in specific regions.
3Ease of manufacture
If metallic electrode directly contacts silicon surface, then manufacturing is simple, but excessive recombination current occurs at contact region
Solution Approach 1:
The tunnel oxide layer and polysilicon film are introduced as intermediary layers between the metallic electrode and the silicon surface in the contact region. These layers provide necessary passivation to suppress recombination current while maintaining a relatively simple manufacturing process through selective application techniques.
Solution Approach 2:
Instead of applying passivation layers across the entire surface, the invention applies them partially only to the contact region where recombination occurs. This partial action maintains manufacturing simplicity while effectively addressing the recombination problem only where needed, avoiding unnecessary complexity in light absorption regions.
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 structure effectively suppresses recombination at the surface, improves light absorption efficiency, and is compatible with conventional mass production techniques, enabling rapid efficiency improvements and cost reductions in crystalline-silicon photovoltaic cells.
Implementation Method 1
Surface passivation techniques for photovoltaic crystalline silicon is growing mature, and a degree of the passivation approaches its maximum
Implementation Method 2
a silicon-based film has strong absorption on sunlight
Data Source
Figure 1~2
AI summary
A partial tunneling oxide layer passivation contact structure of a photovoltaic cell and a photovoltaic module, wherein the partial tunneling oxide layer passivation contact structure of the photovoltaic cell comprises a cell body, a first tunneling oxide layer disposed on the surface of the cell body, and a first polysilicon thin film layer disposed on the surface of the tunneling oxide layer, wherein the surface of the cell body comprises a passivation contact area and a light absorption area, the first tunneling oxide layer is arranged in the passivation contact area, and the projection of the first polysilicon film layer on the surface of the cell body is in the passivation contact area. The first tunneling oxide layer and the first polysilicon thin film layer only cover the passivation contact area, which improves the passivation level in this area and reduces the recombination of the cell surface, however, the first tunneling oxide layer and the first polysilicon film layer are not in the light absorption area, that is, a non-metal contact area, which reduces the shielding of sunlight and improves the light absorption efficiency.