Solar Cell Silicon Substrate Heat Treatment for Oxygen Defect Control
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Solution Overview
Problem
Thermal treatment of silicon single crystal substrates at 800°C or more leads to oxygen-induced defects, degrading the minority carrier lifetime and solar cell characteristics, especially with higher oxygen concentrations.
Innovation Solution
A method involving high temperature thermal treatment at 1200°C or more for 30 seconds or more before low temperature thermal treatment between 800°C and 1200°C to dissolve oxide precipitate nuclei, preventing oxygen-induced defects and improving solar cell conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If thermal treatment is performed at 800°C or more to form oxide films or perform dopant diffusion, then the substrate undergoes necessary manufacturing processes, but oxygen-induced defects grow and minority carrier lifetime decreases
Solution Approach 1:
The patent applies preliminary action by performing high-temperature thermal treatment (1200°C or more for 30 seconds or more) before the low-temperature thermal treatment (800°C to less than 1200°C). This preliminary high-temperature treatment dissolves oxide precipitate nuclei in advance, preventing their growth during subsequent manufacturing processes. As a result, the substrate can undergo necessary thermal treatments for oxide film formation or dopant diffusion without developing oxygen-induced defects, thereby maintaining minority carrier lifetime while enabling ease of manufacture.
2Quantity of substance
If high oxygen concentration is present in the silicon single crystal substrate, then the substrate can be manufactured with certain properties, but oxygen-induced defects grow more readily and degrade solar cell characteristics
Solution Approach 1:
The patent converts the harmful effect of high oxygen concentration into a beneficial outcome. By performing high-temperature thermal treatment (1200°C or more for 30 seconds or more) before low-temperature treatment, the oxide precipitate nuclei formed due to high oxygen concentration are dissolved rather than allowed to grow. This transforms the potential harm of high oxygen content into an opportunity to create a substrate with high oxygen concentration but without oxygen-induced defects, thereby maintaining good solar cell characteristics.
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 effectively prevents the decrease in minority carrier lifetime, enhancing the conversion efficiency of solar cells by dissolving oxide precipitate nuclei, thereby improving the substrate quality even with higher oxygen concentrations.
Implementation Method 1
subjecting the silicon single crystal ingot or the silicon substrate to high temperature thermal treatment at a temperature of 1200° C. or more for 30 seconds or more
Implementation Method 2
it is possible to previously dissolve oxide precipitate nuclei, which can be origins of oxide precipitation defects
Implementation Method 3
the emitter layer is formed by vapor-phase diffusion of POCl3 or coating diffusion of phosphoric acid-base material
Implementation Method 4
forming an oxide film on the substrate surface
Data Source
AI summary
The present invention is a method for manufacturing a substrate for a solar cell composed of a single crystal silicon, including the steps of: producing a silicon single crystal ingot; slicing a silicon substrate from the silicon single crystal ingot; and subjecting the silicon substrate to low temperature thermal treatment at a temperature of 800° C. or more and less than 1200° C., wherein the silicon single crystal ingot or the silicon substrate is subjected to high temperature thermal treatment at a temperature of 1200° C. or more for 30 seconds or more before the low temperature thermal treatment. As a result, it is possible to provide a method for manufacturing a substrate for a solar cell that can prevent decrease in the minority carrier lifetime of the substrate even when the substrate has higher oxygen concentration.