Thrust 2: Organic Electronics
CMDITR researchers have developed technology to fabricate large-area organic solar cells.
Thrust 2 Overview
The mission of this thrust is to advance the science and engineering of organic-based nanostructured materials and devices with an emphasis on their electrical properties (conducting, dielectric, and semiconducting), and their optoelectronic properties (photovoltaic and photodetection).
Our research aims at developing a new material platform for printed electronics on flexible substrates that will enable technological innovations in applications that require smart functions at low cost, on large areas, and at low power. The approach is to exploit new chemistries to control and improve charge transport, charge injection, light harvesting for the processing, storage, sensing, exchange, and display of information.
The research within Thrust 2 is organized into two major science and technology areas, one on printable organic-field-effect transistors, and another on flexible portable photovoltaic cells combined with packaging and patterning technologies:
Printable Field-Effect Transistors for Smart Integrated Platforms
STA 3 is comprised of one main research project:
- Project 3.1: Organic and metal oxide field effect transistors for flexible electronics
Objectives:Develop an organic material technology platform to fabricate low cost, large area, self-powered printable electronic circuits and sensors on plastic substrates. This research area is undergoing rapid development and is generating increased industrial interest. This momentum is due to the recent maturing of organic electronic technologies and their strong potential for ultra low-cost, large-area devices. Areas of particular interest are drivers for electronic paper, drivers for large area displays, organic image sensors, radio-frequency identification (RFID) tags for applications in transportation, manufacturing and logistics, security/access control, animal tracking, and other emerging wireless sensing technologies.
Approach:The development of the multiple components required to develop organic circuitry is a challenging task that requires a multidisciplinary approach. It involves the synthesis of organic and hybrid semiconductors, dielectrics, and conductors, their processing, the characterization and modeling of the material's optical and electrical bulk properties, and the characterization and modeling of the current voltage characteristics of basic components such as resistors, capacitors, diodes, photodiodes, and field-effect transistors. The fabrication and demonstration of circuits is assisted by the development of programs similar to those used for the design of traditional silicon-based devices to predict the performance of elementary circuits such as logic gates, active filters, and ring oscillators. A key requirement to advance printable electronic technologies is the development of thermally stable, high-mobility organic and hybrid materials with both hole and electron mobilities higher than those of amorphous silicon (> 1 cm²/Vs). a-Si is an n-type semiconductor which limits the design of NMOS circuits. The performance of p-channel a-Si devices is two orders of magnitude lower and does not allow the preferred complementary design (CMOS) of circuits.
Organic Portable Power Generation
STA 4 is organized into two main research projects:
- Project 4.1: Organic solar cells and integrated modules
- Project 4.2: Packaging and processing for printed electronics
- To advance the understanding of the physics that governs the operation of organic solar cells and to develop models that can be used to guide the optimization of their performance. These models also guide the synthesis of new materials for photovoltaic devices with optimized electrical and optical properties.
- To increase the efficiency of devices based on bulk heterojunctions and multilayer geometries by the synthesis of new molecules and polymers with optimized properties.
- To study the reliability of these devices and develop new transparent conducting layers intended as replacements for ITO, which is expensive and has limited mechanical properties when deposited on flexible organic substrates.
- Packaging research is focusing simultaneously on providing good barriers to moisture and oxygen, and on characterizing and modeling the mechanical performance of flexible solar cells.
- To understand the limiting factors when the area of the cells is increased and to develop means to develop high efficiency large area cells and modules.
- To develop new patterning and processing techniques with high resolution such as thermochemical nanolithography (TCNL).
Approach: The development of organic solar cells and modules with high power conversion efficiency requires a multidisciplinary approach that involves new material synthesis, optical, electrical and morphological characterization, device fabrication, testing and modeling. Two types of approaches are used currently within the Center to develop organic solar cells: (i) a multilayer geometry that requires materials with large excitonic diffusion lengths that are processed from the vapor phase; and (ii) donor/acceptor bulk heterojunctions that require nanoscale phase separation and that can be processed from solution.