Solar Cell Metallization with Laser Reverse-Bias Contact Formation
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Solution Overview
Problem
Conventional solar cell preparation methods result in poor photovoltaic conversion performance due to inadequate metallization processes.
Innovation Solution
A method involving laser processing of grid line electrodes and adjacent regions with reverse current application to reverse bias the PN junction, forming metal micelles that reduce contact impedance and enhance photoelectric conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional sintering process is used to form metal paste on silicon wafer surface, then metallization is achieved, but photoelectric conversion performance deteriorates
Solution Approach 1:
The patent applies reverse bias voltage to the PN junction during laser processing, changing the electrical parameter state of the junction. This reverse bias condition modifies the carrier distribution and enables improved metal contact formation without compromising photoelectric conversion performance. The parameter change (applying reverse voltage) transforms the metallization outcome from poor to excellent contact quality.
Solution Approach 2:
The patent employs pulsed laser processing rather than continuous heating. The periodic laser pulses with specific duty cycles allow controlled heating and cooling cycles, enabling metal paste to penetrate the passivation layer and form good contacts while preventing excessive thermal damage to the silicon wafer and maintaining high photoelectric conversion efficiency.
2Reliability
If metal paste is sintered to penetrate passivation layer for electrical contact, then conductivity is improved, but contact impedance remains high
Solution Approach 1:
By applying reverse bias voltage during the sintering process, the patent changes the electrical parameters of the PN junction, creating conditions that facilitate lower contact impedance. The reverse bias state modifies the depletion region and carrier distribution, enabling better electrical contact between the metal paste and the silicon substrate, thus reducing contact impedance while maintaining good electrical contact quality.
3Manufacturing precision
If laser processing is applied to grid line electrodes with reverse current, then filling factor improves, but process complexity increases
Solution Approach 1:
The patent combines multiple functions into a single laser processing step: heating the metal paste for sintering, applying reverse bias voltage to modify electrical characteristics, and forming low-impedance contacts all occur simultaneously during one laser processing operation. This merging of heating, electrical biasing, and contact formation processes achieves improved filling factor and contact quality while limiting the increase in overall system complexity.
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
Improves the filling factor and photoelectric conversion efficiency of solar cells by creating conductive contact points in the doped layer and passivation layer.
Implementation Method 1
performing laser processing on the first grid line electrodes and the adjacent region of the first grid line electrodes
Implementation Method 2
a reverse current is applied between the first grid line electrodes and the second grid line electrodes to reverse bias the PN junction
Implementation Method 3
a reverse current is applied between the first grid line electrodes and the second grid line electrodes to reverse bias the PN junction
Implementation Method 4
the metallization process includes a sintering operation to sinter metal paste printed on the surface of the silicon wafer
Data Source
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AI summary
Method for preparing a solar cell, wherein the method includes providing a substrate, forming a doped layer and a first passivation layer stacked sequentially in a direction away from the substrate on a first surface of the substrate, where the doped layer forms a PN junction with the substrate; forming a second passivation layer on the second surface; forming multiple first grid line electrodes arranged at intervals on the surface of the first passivation layer away from the substrate by performing a sintering process on a surface of the first passivation layer away from the substrate, and forming multiple second grid line electrodes arranged at intervals on the surface of the second passivation layer away from the substrate by performing a sintering process on a surface of the second passivation layer away from the substrate; performing a laser processing on the multiple first grid line electrodes and an adjacent region of the multiple first grid line electrodes, and applying a reverse current between the multiple first grid line electrodes and the multiple second grid line electrodes to reverse bias the PN junction in a same processing operation.The method is beneficial for improving the photoelectric conversion performance of the solar cell.