AVS 52nd International Symposium
    Electronic Materials and Processing Thursday Sessions
       Session EM1-ThA

Paper EM1-ThA5
Chemical Vapor Deposition of Thin Films of Electrically Conducting PEDOT

Thursday, November 3, 2005, 3:20 pm, Room 309

Session: Organic and Molecular Optoelectronics
Presenter: J.P. Lock, MIT
Authors: J.P. Lock, MIT
J.L. Lutkenhaus, MIT
N.S. Zacharia, MIT
P.T. Hammond, MIT
K.K. Gleason, MIT
Correspondent: Click to Email
Chemical vapor deposition (CVD) technology, vital to the fabrication of traditional semiconductor devices, is also desirable for next-generation organic devices, particularly for creating layers which are difficult to process by solution methods or for coating substrates which can not tolerate exposure to solvents. In this work, a CVD process has been demonstrated for the deposition of conducting poly-3,4-ethylenedioxythiophene (PEDOT). This CVD process eliminates the need for polystyrene sulfonate (PSS), which is used to disperse PEDOT in water, but has been identified as a possible source of corrosion in OLEDs leading to shortened device lifetimes. The CVD PEDOT films range from 50 nm to several microns in thickness. Fourier transform infrared spectroscopy confirms the similarity in chemical structure of PEDOT synthesized by CVD and solution techniques. An electrical conductivity as high as 4.37 S/cm has been achieved. The CVD process utilizes a modest stage temperature and results in conformal coatings of high surface area features like fibers and pores. This combination of characteristics has allowed PEDOT deposition onto paper and fabrics to be demonstrated. Conformal coating of microporous or fibrous materials by CVD PEDOT has the potential to lead to better efficiencies in organic devices with high effective surface areas including photovoltaics. Reversible electrochromic responses of CVD PEDOT have been observed as well. The light blue films in their as-deposited state turn darker blue upon electrochemical reduction. The maximum contrast to date is 16.5% with a switching speed of 27 msec for a film having a thickness of 50 nm.