Capacitor Work Function Modifiers Reduce Charging Time
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Solution Overview
Problem
Solid electrolytic capacitors exhibit anomalous charging behavior due to high work function of conductive polymer layers, leading to prolonged charging times, which is not effectively addressed by previous methods focusing on PSS mobility or delamination.
Innovation Solution
Incorporating work function modifiers between conductive polymer layers and adjacent layers to reduce the work function, specifically through materials that interact with surface PSS, forming bonds or mixed layers to decrease surface charge density and electron blocking effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductive polymer layers with high work function are used, then good conductivity and film forming properties are achieved, but charging time is prolonged
Solution Approach 1:
The patent introduces work function modifier layers (such as PEDOT:PSS with controlled PSS content, or layers containing indium oxide, zinc oxide, or other metal oxides) as intermediary layers between the conductive polymer and adjacent layers. These intermediary layers reduce the work function at the interface without compromising the overall conductivity of the capacitor structure, thereby reducing charging time while maintaining good conductivity.
Solution Approach 2:
The patent modifies the work function parameter of the conductive polymer layer by controlling the PSS content, treating with moisture, or applying post-deposition treatments. By changing the work function from high (5.65 eV) to lower values through these parameter adjustments, the charging time is reduced while maintaining the necessary conductivity for capacitor operation.
2Loss of time
If surface PSS concentration is increased, then work function is reduced, but electron blocking effects increase
Solution Approach 1:
The patent applies local quality by creating regions with different PSS concentrations at specific locations within the conductive polymer layer. The surface regions have higher PSS concentration to reduce work function and charging time, while bulk regions maintain lower PSS concentration to avoid excessive electron blocking. This spatial variation in composition optimizes both charging speed and electron transport.
Solution Approach 2:
The patent uses composite materials combining conductive polymer (PEDOT) with controlled amounts of PSS, and further复合 with metal oxides (indium oxide, zinc oxide, tin oxide) or other work function modifiers. This composite structure allows the PSS-rich surface regions to reduce work function while the metal oxide components and polymer matrix prevent excessive electron blocking, achieving both fast charging and good electron transport.
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
The use of work function modifiers significantly reduces charging time, achieving times close to theoretical limits, with capacitors having charging times no more than 1.5 times the theoretical limit, and in some cases, equal to or less than the theoretical limit.
Implementation Method 1
materials that interact with surface PSS, forming bonds or mixed layers to decrease surface charge density and electron blocking effects
Implementation Method 2
Incorporating work function modifiers between conductive polymer layers and adjacent layers to reduce the work function, specifically through materials that interact with surface PSS
Data Source
AI summary
A capacitor, and method for making the capacitor, is provided with improved charging characteristics. The capacitor has an anode, a cathode comprising a conductive polymer layer and a work function modifier layer adjacent the conductive polymer layer and a dielectric layer between the anode and the cathode.