TOPCon Solar Cell Contacts With Low-Power Laser Scanning
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Solution Overview
Problem
The traditional method for making tunnel oxide passivating contacts (TOPCon) solar cells faces challenges in reducing contact resistance between metal grid lines and the silicon substrate, which limits conversion efficiency due to damage from high laser power during laser selective emitter (LSE) processing.
Innovation Solution
The method employs laser-enhanced contact optimization (LECO) technology to form ohmic contacts between metal and silicon without damaging the passivation layer, eliminating the need for LSE and combining boron diffusion with high-temperature oxidation, allowing for improved contact resistance and efficiency without additional doping steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high laser power is used during laser selective emitter (LSE) processing to reduce contact resistance, then contact resistance between metal grid lines and silicon substrate is reduced, but the passivation layer is damaged
Solution Approach 1:
The patent changes the parameter of laser power from high to low, and introduces a new parameter of repeated scanning. By using low power laser multiple times instead of high power once, the total energy is controlled to avoid passivation layer damage while still achieving contact resistance reduction through cumulative thermal effect
Solution Approach 2:
The patent applies periodic action by repeatedly scanning the metal grid lines multiple times with low power laser. This periodic low-power exposure allows gradual heating and contact resistance reduction without exceeding the damage threshold of the passivation layer in any single exposure
2Reliability
If laser selective emitter (LSE) processing is used to improve contact resistance, then contact resistance is reduced, but additional doping steps are required
Solution Approach 1:
The patent extracts and removes the LSE processing step from the manufacturing process. By using low power laser repeated scanning, the patent achieves contact resistance reduction without requiring the additional doping steps that LSE would require, thereby simplifying the device structure and manufacturing process
3Manufacturing precision
If boron diffusion and high-temperature oxidation are performed separately, then each process can be optimized, but process time increases
Solution Approach 1:
The patent merges boron diffusion and high-temperature oxidation into a single integrated process step. By combining these two previously separate processes, the patent maintains the ability to optimize each process parameter while significantly reducing the total process time and eliminating the need for separate process equipment
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 reduces contact resistance, enhances conversion efficiency, and saves process time by integrating boron diffusion and high-temperature oxidation, while maintaining a wide sintering temperature window and precise control, leading to improved cell performance and reduced manufacturing costs.
Implementation Method 1
maintaining a deflection voltage applied on the solar cell, and using a laser to scan the metal grid lines on the first surface of the silicon substrate
Implementation Method 2
The ultra-thin silicon oxide layer of TOPCon cell utilizes quantum tunneling effect, which allows majority carriers to tunnel and blocks minority carrier to pass
Implementation Method 3
combining boron diffusion with high-temperature oxidation
Data Source
AI summary
A method for making a solar cell includes: providing and texturing a silicon substrate including a first surface and a second surface opposite to the first surface; performing boron diffusion and high-temperature oxidation treatment on the silicon substrate; forming a tunnel oxide layer and a doped polycrystalline silicon layer on a second surface; depositing a passivation layer on the first surface or both the first surface and the second surface; depositing anti-reflection layers on the first and second surfaces; forming metal grid lines on both the first and second surfaces to form a solar sheet; applying a deflection voltage to the solar sheet; maintaining the deflection voltage and using laser to scan the metal grid lines on the first surface.