Conjugated polymers: paving the way for next-generation electronics and photonics

Conjugated polymers (CPs) have emerged as a promising class of materials in modern electronics and photonics, offering unique advantages over traditional inorganic semiconductors. Their delocalized π-electron systems provide high flexibility, tunable electronic properties, and solution processability, making them ideal for a wide range of applications. A comprehensive review published in Nano-Micro Letters by researchers from Khalifa University, led by Professor Ammar Nayfeh and Professor Dinesh Shetty, explores the evolving role of CPs in nanoelectronics and photonics, highlighting recent advancements and future prospects.

Why Conjugated Polymers Matter

• Versatile Electronic Properties: CPs can be engineered to exhibit a wide range of electronic properties, making them suitable for various applications, including organic photovoltaics (OPVs), organic field-effect transistors (OFETs), and nonvolatile memory devices.
• Solution Processability: The ability to process CPs from solution enables low-cost, large-area fabrication techniques, such as roll-to-roll printing, which are highly desirable for commercial applications.
• Mechanical Flexibility: Unlike rigid inorganic semiconductors, CPs are mechanically flexible, opening up opportunities for flexible and wearable electronics.

Molecular Engineering and Design Strategies

• Backbone and Side-Chain Engineering: By manipulating the polymer backbone and side chains, researchers can fine-tune the electronic properties of CPs. For example, introducing electron-donating or electron-withdrawing groups can adjust the bandgap and charge carrier mobility.
• Donor-Acceptor Architectures: The use of donor-acceptor (D-A) structures in CPs enhances their performance in photovoltaic applications by improving charge separation and transport. Recent advancements have led to OPVs with efficiencies approaching 20%.
• Two-Dimensional (2D) CPs: 2D CPs offer extended π-conjugation and enhanced charge transport properties, making them attractive for applications such as organic FETs and memristors.

Applications in Electronics and Photonics

Photovoltaics

• High Efficiency and Stability: Recent research has focused on improving the efficiency and stability of OPVs through molecular engineering. For example, the incorporation of naphthalene diimide (NDI)-based acceptors and asymmetric side-chain engineering has led to significant performance enhancements.
• Single-Component Organic Solar Cells (SCOSCs): SCOSCs based on conjugated block copolymers (CBCs) or double-cable conjugated polymers (DCCPs) have shown promising results, with efficiencies exceeding 14%. These devices offer improved stability and reduced phase separation compared to traditional bulk heterojunctions.

Electronic Devices

• OFETs and OECTs: Advances in CPs have led to the development of high-performance OFETs and organic electrochemical transistors (OECTs). For example, the use of covalent organic frameworks (COFs) and ladder-type polymers has resulted in OFETs with high mobility and stability.
• Nonvolatile Memory Devices: CPs have been integrated into various memory devices, including charge-trapping memories (CTMs) and resistive random-access memories (ReRAMs). Recent innovations include the use of 2D CPs and metal-coordinated polymers to enhance memory performance and stability.

Future Outlook

• Scalability and Commercialization: Realizing the full potential of CPs requires addressing challenges related to scalability and cost. Developing scalable, low-cost fabrication techniques, such as roll-to-roll processing, will be crucial for commercial adoption.
• Environmental Stability: Improving the long-term stability of CP-based devices under environmental conditions, such as humidity and UV exposure, is essential for practical applications. Multilayer encapsulation and the development of more stable CPs are active areas of research.
• Emerging Applications: The unique properties of CPs open up opportunities for emerging applications, such as bioelectronics, neuromorphic computing, and sustainable energy solutions. Continued research in molecular engineering and device architecture will drive the development of next-generation technologies.

Stay tuned for more groundbreaking advancements in the field of conjugated polymers as researchers continue to push the boundaries of what is possible in electronics and photonics!