N-Type Semiconductor Layer Using Onium Salt Dopant
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Solution Overview
Problem
Current n-type thermoelectric conversion materials face challenges in achieving balanced electric conductivity and Seebeck coefficient, leading to a reduced figure of merit Z, particularly when using carbon nanotubes as nanocarbon materials, where excessive doping and high thermal conductivity hinder performance improvements.
Innovation Solution
The use of an onium salt represented by a specific formula, with an anionic portion having weak nucleophilicity, such as Cl−, Br−, or I−, as a dopant for carbon nanotubes, inhibits excessive doping, thereby achieving a high Seebeck coefficient and low thermal conductivity, enhancing the figure of merit Z.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional onium salts (e.g., tetrabutylammonium hydroxide) are used as dopants for carbon nanotubes, then electric conductivity is improved, but Seebeck coefficient is reduced and thermal conductivity increases excessively
Solution Approach 1:
The patent changes the chemical parameters of the dopant by selecting onium salts with specific anionic portions having weak nucleophilicity (Cl−, Br−, or I−). This parameter change in the dopant's chemical properties prevents excessive doping of carbon nanotubes, thereby maintaining low thermal conductivity while achieving appropriate electric conductivity, ultimately improving the figure of merit Z
Solution Approach 2:
The onium salt acts as an intermediary substance that mediates the doping process of carbon nanotubes. By using onium salts with weakly nucleophilic anions as intermediaries, the patent achieves controlled doping that improves electric conductivity without causing excessive doping that would increase thermal conductivity, thus resolving the contradiction between these two parameters
2Reliability
If doping level is increased to improve electric conductivity, then electric conductivity increases, but thermal conductivity increases proportionally, reducing figure of merit Z
Solution Approach 1:
The patent changes the chemical parameter of the dopant (nucleophilicity of anionic portion) to achieve selective doping control. By using onium salts with weakly nucleophilic anions, the doping level is controlled to improve electric conductivity without proportionally increasing thermal conductivity, thus improving the figure of merit Z
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 results in an n-type semiconductor layer with improved thermoelectric conversion performance, characterized by balanced electric conductivity and Seebeck coefficient, leading to a higher figure of merit Z, while maintaining stability against environmental influences like moisture.
Implementation Method 1
adding a tetrabutylammonium hydroxide salt (onium salt) to CNT
Implementation Method 2
Thermoelectric conversion elements can convert thermal energy directly into electric power
Data Source
AI summary
An object of the present invention is to provide a semiconductor layer (n-type semiconductor layer) which demonstrate an excellent thermoelectric conversion performance and exhibits n-type characteristics. Another object of the present invention is to provide a thermoelectric conversion layer formed of the n-type semiconductor layer and a composition for forming an n-type semiconductor layer. Still another object of the present invention is to provide a thermoelectric conversion element, which has the thermoelectric conversion layer as an n-type thermoelectric conversion layer, and a thermoelectric conversion module.The n-type semiconductor layer of the embodiment of the present invention contains a nanocarbon material and an onium salt represented by a specific structure.