CAREER: Charge Injection in Polymers and Small Organic Molecules

Cornell University, Ithaca NY

Investigators

Abstract

This CAREER project aims to advance fundamental understanding of organic interfaces, and to provide a unique environment to prepare students for careers in the rapidly growing area of or-ganic optoelectronics. In devices such as light emitting diodes, thin film transistors, photodiodes and photorefractives, a primary problem limiting the ability to improve performance and stability is lack of a fundamental understanding of the interface between organic materials and metal electrodes. Achieving a fundamental understanding of carrier transport across these interfaces, identifying and understanding the primary mechanisms of degradation at these interfaces, and then utilizing this understanding to improve the electrical properties are the scientific/engineering issues being addressed in this project. A series of experiments seeking to elucidate the mecha-nism of charge injection at metal/organic interfaces and leading to improvement of the perform-ance and stability of metal/organic contacts will be conducted. The approach is to first establish the dependence of injection on electric field, temperature and materials parameters such as layer thickness, dielectric constant, energy barrier and the presence of traps, at model metal/organic interfaces. These interfaces will be formed by depositing organic materials with well-characterized charge transport properties on properly chosen metals. Second, doping of the or-ganic will be induced by the introduction of appropriate thin conducting layers at the interface and its influence on injection investigated. A variety of experimental techniques will be used to probe the nature of these interfaces and contact properties. Finally, the stability of both pristine and doped interfaces will be studied with accelerated aging tests in order to deduce primary modes of degradation and determine their influence on injection. The research project will be closely integrated with an education and outreach program incorpo-rating both conventional courses and extensive mentoring. New courses will be developed to provide undergraduate and graduate students with a solid background in organic optoelectronics. In addition to graduate research assistants, undergraduate students will be intimately involved in the research program - providing them with a unique opportunity to complement their theoretical training with hands-on research activities. A greater community focusing on organic optoelec-tronics will be assembled from diverse groups across the campus and other universities, which will give students the opportunity to experience a truly multidisciplinary environment. Also, an extended outreach program aimed at K-12, female/minority colleges, and industry, will be devel-oped to extend these benefits to the broad community. The proposed program will create a center of excellence in research and education at Cornell that will benefit the field of organic optoelec-tronics and society at large. The broad education and outreach plan will establish a unique envi-ronment expected to attract students to sciences and nurture the researchers that will shape the future of organic optoelectronics. %%% The project addresses fundamental research issues in a topical area of materials science having high technological relevance. The scope of the project will expose students to challenges in materials synthesis, processing, and characterization. An important feature of the project is the strong emphasis on education, and the integration of research and education. ***