Graded Dopant Profile in Amorphous Silicon Photovoltaic Devices
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Solution Overview
Problem
In photovoltaic devices with amorphous silicon layers on crystalline silicon substrates, there is a need to reduce recombination centers at the interface and minimize carrier disappearance due to recombination, while also reducing series resistance in the vicinity of the interface.
Innovation Solution
A photovoltaic device with a crystalline semiconductor substrate and an amorphous semiconductor layer, featuring a p-type dopant density profile that decreases stepwise in the film thickness direction from the interface with the substrate, which is achieved by introducing boron and oxygen during the film formation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxygen is introduced into the interface portion between the silicon substrate and the intrinsic amorphous silicon layer, then interface characteristics are improved and carrier recombination is suppressed, but series resistance component cannot be reduced sufficiently
Solution Approach 1:
The patent applies local quality by creating a graded dopant concentration profile where the dopant concentration varies spatially within the amorphous silicon layer. Specifically, the dopant concentration is highest at the interface with the crystalline silicon substrate and decreases toward the opposite surface, allowing different regions to have optimized properties: high conductivity at the interface and appropriate electrical characteristics in the bulk layer.
Solution Approach 2:
The patent employs parameter changes by systematically varying the dopant concentration parameter throughout the amorphous silicon layer thickness. The dopant concentration is changed from a uniform distribution to a graded distribution that decreases from the substrate interface toward the free surface, thereby optimizing both conductivity and recombination suppression simultaneously.
2Reliability
If a substantial intrinsic amorphous silicon layer is formed between the crystalline silicon substrate and the doped amorphous silicon layer, then carrier recombination is suppressed, but electrical conductivity in the vicinity of the interface is reduced
Solution Approach 1:
The patent applies local quality by creating a graded dopant concentration profile where the dopant concentration varies spatially within the amorphous silicon layer. Specifically, the dopant concentration is highest at the interface with the crystalline silicon substrate and decreases toward the opposite surface, allowing different regions to have optimized properties: high conductivity at the interface and appropriate electrical characteristics in the bulk layer.
Solution Approach 2:
The patent employs parameter changes by systematically varying the dopant concentration parameter throughout the amorphous silicon layer thickness. The dopant concentration is changed from a uniform distribution to a graded distribution that decreases from the substrate interface toward the free surface, thereby optimizing both conductivity and recombination suppression simultaneously.
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 configuration enhances photoelectric conversion efficiency by improving the electrical conductivity and reducing recombination centers, leading to increased fill factor and output power in the photovoltaic device.
Implementation Method 1
a p-type dopant density profile at an interface between the substrate and the amorphous semiconductor layer, the profile decreasing stepwise in a film thickness direction from the vicinity of the interface with the substrate
Implementation Method 2
photovoltaic device which includes a crystalline semiconductor substrate and an amorphous semiconductor layer formed on a main surface of the substrate
Data Source
AI summary
This photovoltaic device is provided with a crystalline semiconductor substrate, and a first amorphous layer formed on the main surface of the substrate. At the interface between the substrate and the first amorphous layer, electrical conductivity can be improved while suppressing an increase in recombination centers, and power generation efficiency can be improved by having a p-type dopant density profile that decreases stepwise in the film thickness direction from the vicinity of the interface with the substrate.