Graphene Electrodes with PEDOT via Oxidative CVD
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Solution Overview
Problem
The integration of graphene as a transparent conducting electrode in organic photovoltaics is hindered by the low work function of graphene, which creates an energy barrier with common electron donor materials, and the application of conductive polymers like PEDOT:PSS is challenging due to graphene's hydrophobic nature and the damaging effects of plasma treatments.
Innovation Solution
The use of oxidative chemical vapor deposition (oCVD) to form a conductive polymer, such as PEDOT, directly on graphene substrates, which avoids solution processing steps that can damage graphene and allows for conformal, uniform deposition without introducing defects or shorting pathways, enabling efficient energy level alignment and improved device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If plasma treatment is applied to render graphene surface hydrophilic, then PEDOT:PSS coverage is improved, but graphene conductivity is greatly reduced
Solution Approach 1:
The patent uses O2 plasma treatment as an intermediary process that temporarily modifies the graphene surface to enable conformal PEDOT:PSS deposition, while the subsequent annealing step restores the graphene's electrical properties by removing plasma-induced damage
Solution Approach 2:
The patent applies O2 plasma treatment as a preliminary surface preparation step before depositing PEDOT:PSS, creating a hydrophilic surface that enables conformal coverage. This preliminary action is followed by annealing to restore conductivity
2Ease of manufacture
If solution processing is used to apply conductive polymer on graphene, then deposition is simplified, but graphene is damaged
Solution Approach 1:
The patent replaces mechanical solution processing with vapor-phase deposition, where PEDOT is deposited from the vapor phase onto the graphene surface, avoiding direct contact with liquid solvents that could damage the graphene structure
Solution Approach 2:
The patent utilizes phase transition of PEDOT from vapor phase to solid film during deposition, allowing conformal coating of graphene without liquid solvent exposure. The vapor-phase deposition enables direct transition from gaseous monomer to polymeric film on the graphene surface
3Reliability
If graphene is used as transparent conducting electrode, then mechanical robustness and transparency are maintained, but energy level alignment with electron donor material is poor
Solution Approach 1:
The patent introduces PEDOT as an intermediary layer between graphene and the electron donor material, serving as a buffer that improves energy level alignment and facilitates charge transfer while maintaining the mechanical and optical benefits of graphene
Solution Approach 2:
The patent creates a composite electrode structure combining graphene and PEDOT, where the two materials work synergistically - graphene provides mechanical robustness and transparency, while PEDOT provides improved energy level alignment and charge transfer properties
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 method achieves power conversion efficiencies of at least 3.0% in small molecule organic photovoltaic devices, comparable to those using indium tin oxide (ITO) counterparts, with improved charge transfer and reduced transmission losses, while maintaining the mechanical robustness and transparency of graphene electrodes.
Implementation Method 1
poly(3,4-ethylenedioxythiophene) (PEDOT) formed on at least a portion of the graphene, wherein the PEDOT is formed by oxidative chemical vapor deposition
Data Source
AI summary
The present invention generally relates to devices comprising graphene and a conductive polymer (e.g., poly(3,4-ethylenedioxythiophene) (PEDOT)), and related systems and methods. In some embodiments, the conductive polymer is formed by oxidative chemical vapor deposition.