TOPCon Solar Cell Barrier Layers for Passivation and Light Absorption
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Solution Overview
Problem
The existing TOPCon cells face issues with parasitic light absorption and reduced passivation effects due to thick polycrystalline silicon layers and high-temperature sintering processes, leading to decreased photoelectric conversion efficiency.
Innovation Solution
A solar cell design incorporating a hydrogen barrier layer and metal barrier layer within a grid-shaped doped conductive structure, which prevents hydrogen overflow and electrode erosion, respectively, enhancing passivation and reducing the thickness of the polycrystalline silicon layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the polycrystalline silicon layer is thickened to improve passivation loss caused by metallization process, then passivation effect is improved, but parasitic light absorption increases
Solution Approach 1:
The patent applies local quality by creating a non-uniform doping concentration distribution within the polycrystalline silicon layer. The doping concentration is higher near the tunnel oxide interface (improving passivation) and gradually decreases toward the rear surface (reducing parasitic light absorption). This gradient doping profile allows different regions of the same layer to serve different functions optimally.
Solution Approach 2:
The patent changes the doping concentration parameter from uniform to graded distribution. By controlling the doping concentration to decrease from the tunnel oxide interface toward the rear surface, the patent simultaneously achieves good passivation effect at the interface and reduced parasitic absorption in the bulk, resolving the contradiction between these two requirements.
2Ease of manufacture
If high-temperature sintering is used in screen printing metallization process, then metallization is achieved, but quality of passivation of phosphorus-doped polycrystalline silicon structure deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-forming the phosphorus-doped polycrystalline silicon structure with optimized doping concentration distribution before the high-temperature sintering process. The doping profile is established in advance to withstand the thermal stress of sintering, ensuring passivation quality is maintained even after exposure to high temperatures during metallization.
Solution Approach 2:
The patent applies preliminary anti-action by designing a doping concentration gradient that anticipates and counteracts the damaging effects of high-temperature sintering. The higher doping concentration near the interface provides a buffer against thermal degradation, preventing passivation quality deterioration during the metallization process.
3Reliability
If silver in finger is used for ohmic contact effect, then electrical contact is achieved, but polycrystalline silicon is eroded to depth of about 30 nm
Solution Approach 1:
The patent applies local quality by concentrating the doping in a localized region near the tunnel oxide interface, creating a highly conductive contact region exactly where the metal finger makes contact. This localized high-doping region provides excellent ohmic contact while minimizing the overall amount of polycrystalline silicon that needs to be present, thereby reducing erosion damage.
Solution Approach 2:
The patent applies preliminary action by pre-forming the heavily doped polycrystalline silicon layer before the metallization process. This pre-formed conductive layer serves as a buffer that protects the underlying semiconductor substrate from direct contact and erosion by the metal fingers, while still providing the necessary ohmic contact effect.
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 design improves fill factor efficiency and solar energy conversion efficiency by maintaining hydrogen concentration at the tunneling layer interface and reducing parasitic light absorption, outperforming conventional TOPCon cells.
Implementation Method 1
The ultra-thin oxide layer may cause electrons to tunnel into the polycrystalline silicon layer and block transport of holes
Implementation Method 2
a hydrogen barrier layer located over a surface of the tunneling layer
Implementation Method 3
a metal barrier layer that are stacked on one another
Implementation Method 4
improves photoelectric conversion efficiency of the solar cell
Data Source
AI summary
A solar cell, a method for manufacturing solar cell, and a photovoltaic module. The solar cell includes: a semiconductor substrate; a tunneling layer located over a rear surface of the semiconductor substrate; a hydrogen barrier layer located over a surface of the tunneling layer; a lightly doped conductive layer located over a surface of the hydrogen barrier layer; and grid-shaped doped conductive layers located on at least part of a surface of the lightly doped conductive layer, wherein each of the grid-shaped doped conductive layers includes a heavily doped conductive layer and a metal barrier layer that are stacked on one another.