Passivated Back Contact Structure for Low-Recombination IBC Solar Cells
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Solution Overview
Problem
Conventional interdigitated back contact (IBC) solar cells face issues such as poor isolation effect, increased recombination, reduced conversion efficiency due to direct contact with the silicon substrate, and scratches during belt transportation, which affect production scalability and efficiency.
Innovation Solution
A passivated contact structure with a porous first passivation layer and a second passivation layer, featuring openings for conductive layer connection, enhances isolation and reduces recombination, while a back contact structure with a protective region prevents scratches during transportation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tunneling layer is used to isolate doped polysilicon from silicon substrate, then passivation effect is improved, but thickness control accuracy deteriorates
Solution Approach 1:
The patent introduces a dielectric layer as an intermediary between the doped polysilicon layer and the silicon substrate. This dielectric layer serves as a tunneling barrier that provides effective passivation while being easier to control in thickness during manufacturing. The dielectric layer material (such as silicon oxide or silicon nitride) can be deposited with well-controlled thickness through standard semiconductor fabrication processes, resolving the contradiction between achieving good passivation effect and maintaining precise thickness control.
Solution Approach 2:
The patent changes the material parameter of the tunneling layer from doped polysilicon to dielectric materials (silicon oxide, silicon nitride, or their combinations). This parameter change allows for better thickness control through conventional deposition techniques while maintaining the essential tunneling function for carrier transport. The dielectric layer can be optimized in thickness (typically 5-50 nm) to balance passivation effectiveness with manufacturing precision.
2Power
If doped polysilicon is directly contacted with silicon substrate, then electrical conductivity is improved, but recombination increases
Solution Approach 1:
The patent introduces a dielectric layer as an intermediary between the doped polysilicon layer and the silicon substrate. This dielectric layer acts as a tunneling barrier that prevents direct contact between the doped polysilicon and silicon substrate, thereby reducing recombination losses at the interface. Meanwhile, the dielectric layer maintains sufficient electrical conductivity for carrier transport through tunneling, thus resolving the contradiction between conductivity and recombination loss.
Solution Approach 2:
The patent employs a thin dielectric layer (5-50 nm) that can be easily deposited and removed or modified in subsequent processing steps. This thin layer provides the necessary tunneling function without creating permanent interface defects that would lead to recombination. The dielectric layer serves its purpose during fabrication and operation, then can be addressed in later processing without affecting the overall device performance.
3Power
If tunneling layer thickness is reduced, then tunneling resistance is reduced, but passivation effect deteriorates
Solution Approach 1:
The patent optimizes the thickness parameter of the dielectric layer to a specific range (5-50 nm) that balances tunneling resistance and passivation effect. This optimized thickness range allows sufficient carrier tunneling while maintaining effective passivation of the silicon substrate surface. The dielectric layer material composition (silicon oxide, silicon nitride, or combinations) is also adjusted to achieve the desired balance between electrical properties and passivation performance.
Solution Approach 2:
The patent uses composite dielectric layer structures (combinations of silicon oxide and silicon nitride layers) to achieve optimal performance. By combining different dielectric materials with complementary properties, the patent can simultaneously optimize tunneling resistance and passivation effect. The composite structure allows for tailored electrical and chemical properties that a single material cannot provide, resolving the contradiction between low resistance and high passivation.
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 proposed structure improves isolation, reduces recombination, and prevents scratches, leading to enhanced conversion efficiency and production scalability by minimizing direct contact and surface pollution.
Implementation Method 1
a first passivated contact region disposed on a silicon substrate, and a second passivated contact region disposed on the first passivated contact region
Implementation Method 2
The second passivated contact region has an opening for a conductive layer to penetrate, so as to be connected to the first passivated contact region
Data Source
AI summary
A cell assembly includes a first doped region. The first doped region includes a first passivated contact region disposed on the silicon substrate, and a second passivated contact region disposed on the first passivated contact region. The first passivated contact region includes a first doped layer, a first passivation layer, and a second doped layer. The second passivated contact region includes a second passivation layer and a third doped layer. The second passivated contact region includes an opening for connecting a conductive layer of the solar cell to the first passivated contact region.