TOPCon Solar Cell Selective Polysilicon Contact for Lower Light Loss
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Solution Overview
Problem
The polysilicon layer in tunnel oxide passivated contact (TOPCon) solar cells exhibits severe parasitic absorption of light, leading to reduced light utilization and current loss, limiting further improvements in open-circuit voltage and conversion efficiency.
Innovation Solution
A solar cell structure is developed with a silicon substrate, a tunnel oxide layer, a first doped polysilicon layer, a laser-absorption layer, and a second doped polysilicon layer, where the laser-absorption layer is vaporized by a laser to remove the second doped polysilicon layer from non-metal contact regions, improving light utilization and reducing charge carrier recombination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick polysilicon layer is formed across the entire surface of the silicon wafer to achieve passivating contact structure, then charge carrier recombination is reduced and contact performance is improved, but light utilization rate is greatly reduced and current loss increases
Solution Approach 1:
The polysilicon layer is segmented into two distinct layers: a first doped polysilicon layer that covers the entire surface for passivation, and a second doped polysilicon layer that is selectively formed only in the metal contact region. This segmentation allows the non-contact regions to have minimal light-absorbing material while the contact region maintains adequate passivation and electrical contact properties.
Solution Approach 2:
Different regions of the solar cell surface are given different polysilicon layer configurations: the metal contact region has a thicker second doped polysilicon layer for optimal electrical contact, while the non-metal contact regions have only the thin first doped polysilicon layer to minimize light absorption. This local differentiation resolves the contradiction between uniform passivation and light utilization.
2Reliability
If a thick polysilicon layer is formed across the entire surface to achieve passivating contact, then charge carrier recombination is reduced, but conversion efficiency is limited
Solution Approach 1:
The polysilicon structure is divided into a first doped polysilicon layer for universal passivation and a second doped polysilicon layer selectively positioned in the metal contact region. This segmentation ensures high passivation quality where needed while minimizing light absorption in non-contact regions, thereby improving overall conversion efficiency.
Solution Approach 2:
The solar cell surface is differentiated into metal contact regions with thicker polysilicon for passivation and non-metal contact regions with thinner polysilicon for light transmission. This local quality differentiation simultaneously achieves high passivation quality and high conversion efficiency by optimizing each region for its specific function.
3Reliability
If a uniform polysilicon layer is formed across the entire surface, then passivation is achieved, but light utilization rate is reduced
Solution Approach 1:
The uniform polysilicon layer is segmented into a first doped polysilicon layer covering the entire surface for passivation and a second doped polysilicon layer selectively formed only in the metal contact region. This segmentation maintains passivation across the entire surface while reducing light absorption in non-contact regions where the second layer is absent.
Solution Approach 2:
Different polysilicon layer thicknesses are applied to different regions: the first doped polysilicon layer provides uniform passivation across the entire surface, while the second doped polysilicon layer is locally applied only to the metal contact region. This local quality approach ensures passivation where needed while maximizing light utilization in non-contact 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 approach enhances the efficiency of the solar cell by improving light utilization and reducing charge carrier recombination, while simplifying the preparation process and reducing costs, making it compatible with existing mass production processes.
Implementation Method 1
a laser-absorption layer disposed on the metal contact region of the surface of the first doped polysilicon layer, the laser-absorption layer is adapted to be vaporized by absorbing a laser having a predetermined wavelength
Implementation Method 2
the laser-absorption layer is adapted to be vaporized by absorbing a laser having a predetermined wavelength
Data Source
Figure 1~2
AI summary
A solar cell, a preparation method thereof, and a photovoltaic module. The solar cell includes a silicon substrate, a tunnel oxide layer, a first doped polysilicon layer, a laser-absorption layer, and a second doped polysilicon layer. The tunnel oxide layer is disposed on a surface of the silicon substrate. The first doped polysilicon layer is disposed on a surface of the tunnel oxide layer. A surface of the first doped polysilicon layer includes a metal contact region and a non-metal contact region. The laser-absorption layer is disposed on the metal contact region of the surface of the first doped polysilicon layer. The laser-absorption layer is adapted to be vaporized by absorbing a laser having a predetermined wavelength. The second doped polysilicon layer is disposed on a surface of the laser-absorption layer.