Step-Shaped Oxygen Profile in Amorphous Silicon Photovoltaic Layers
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Solution Overview
Problem
The optimization of oxygen concentration profiles in intrinsic amorphous silicon layers of photovoltaic devices is needed to improve efficiency, as excessive oxygen can form defects and high-resistance regions, and current methods do not adequately address the specific requirements for different conductive types of semiconductor layers.
Innovation Solution
A photovoltaic device structure with a step-shaped oxygen concentration profile in the intrinsic amorphous silicon layers, where the oxygen concentration is higher near the interface with the semiconductor substrate and decreases within the layer, optimized for both p-type and n-type layers, is implemented using plasma-enhanced chemical vapor deposition (PECVD) to form thin layers with controlled oxygen content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxygen concentration is increased in the intrinsic amorphous silicon layer to improve inactivation and output characteristic, then photovoltaic efficiency is improved, but excessive oxygen forms defects and high-resistance regions that degrade device performance
Solution Approach 1:
The patent applies local quality by creating a non-uniform oxygen concentration distribution within the intrinsic amorphous silicon layer. Specifically, the oxygen concentration is set to be higher near the interface with the doped amorphous silicon layer and lower near the interface with the crystalline silicon substrate. This spatial variation in oxygen concentration allows the layer to simultaneously achieve effective defect inactivation at the doped layer interface while avoiding excessive oxygen accumulation that would create defects and high-resistance regions, thus resolving the technical contradiction between improving photovoltaic efficiency and preventing harmful effects of excessive oxygen.
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 photovoltaic efficiency by effectively inactivating defects at the interface, improving open circuit voltage and maintaining fill factor, while avoiding excessive resistance, thus maximizing power generation efficiency.
Implementation Method 1
a plasma process is utilized to form the intrinsic amorphous silicon layer
Implementation Method 2
an oxygen concentration profile in which a high-oxygen-concentration region is present on a side of the intrinsic amorphous silicon layer near an interface with the semiconductor substrate
Data Source
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AI summary
A photovoltaic device is provided having a semiconductor substrate (10), an i-type amorphous layer (12i) formed over a front surface of the semiconductor substrate (10), a p-type amorphous layer (12p) formed over the i-type amorphous layer (12i), an i-type amorphous layer (16i) formed over a back surface of the semiconductor substrate (10), and an n-type amorphous layer (16n) formed over the i-type amorphous layer (16i). The i-type amorphous layer (12i) and the i-type amorphous layer (16i) have oxygen concentration profiles in which concentrations are reduced in a step-shape from regions near interfaces with the semiconductor substrate (10) and along a thickness direction, and an oxygen concentration in the step-shape portion of the i-type amorphous layer (12i) is higher than an oxygen concentration in the step-shape portion of the i-type amorphous layer (16i).