Synthetic and Mechanistic Studies of Air-Stable Organometallic Dimers as n-Dopants for Organic Electronics

Georgia Tech Research Corporation, Atlanta GA

Investigators

Abstract

TECHNICAL SUMMARY This research project is jointly supported by the Solid State and Materials Chemistry and the Electronic and Photonic Materials Programs. Doping of charge-transport materials can greatly improve the behavior of organic electronic devices. n-Dopants suitable for typical electron-transport materials are inevitably air-sensitive if reacting by simple electron transfer. Approaches in which air-stable precursors form dopants during, or subsequent to, film deposition can simplify device fabrication. The PIs recently demonstrated that air-stable dimers of certain sandwich compounds, such as rhodocene, can n-dope materials, forming the corresponding monomeric sandwich cations. In contrast to other air-stable precursor approaches to molecular n-dopants, side reactions are likely to be minimized and materials with much lower electron affinities (2.8 eV to date) can be doped. This proposal aims to understand the chemistry of these dimers in detail and to broaden their utility. Synthesis, NMR crossover experiments, vis-NIR monitoring of kinetics, and XPS, UPS, and conductivity studies of solution-cast films will be used to establish: the limits of doping using this approach without significantly compromising the dimer air-stability; how the rate can be controlled to permit solution-casting of films in air, with subsequent dopant activation; and the extent to which heavy-metal dimers can be replaced by related dimers of 3d-metal complexes or even all-organic dimers. NON-TECHNICAL SUMMARY There is wide interest in lightweight-flexible electronic devices (displays, lighting, solar cells), that can be made at low cost and low temperature. These use organic (carbon-containing) molecules or polymers in place of traditional semiconductors, the electrical properties of which can be greatly improved using dopants, which increase (n) or decrease (p) the number of electrons in the material. n-Dopants are generally highly reactive, which complicates their use. The PIs have discovered n-dopants that are unusually stable, yet dope many materials. This program will enable an improved understanding and control of these dopants, related dopants, and their reactivity, and may lead to more efficient devices. Students will be trained in organic electronic materials, and, more generally, in investigating scientific problems, and case-studies will be used in the PIs' lectures. The PIs will educate and train women and underrepresented minorities by: hosting summer students and encouraging their application to graduate school, recruiting via seminars at HBCUs and other minority-serving institutions, and attending workshops and conferences with significant minority participation. The PIs' work with a NSF PREM at New Mexico Highlands University, a minority-serving institution, will be supported; students there will determine the structures of new dopants, and the PIs will give lectures linking chemistry and applications.