Correlation between near infrared-visible absorption, intrinsic local and global sheet resistance of poly(3,4-ethylenedioxy-thiophene) poly(styrene sulfonate) thin films

Abstract

The ordinary dielectric function of poly(3,4-ethylenedioxy-thiophene) poly(styrene sulfonate) (PEDOT:PSS) thin films was measured using a combination of spectroscopic ellipsometry and photothermal deflection spectroscopy. This method combination allows for a highly sensitive optical characterization of thin films. Hence, even the detection of weak sub-bandgap and intra-band absorptions is enabled. These intraband transitions of free charge carriers were modeled using a Drude-type oscillator to derive an intrinsic resistances for PEDOT:PSS. These optically derived resistances were compared with those determined by a 4-probe measurement setup for two different types of PEDOT:PSS and for varied annealing temperatures. Good agreement between optical and electrical measurements could be obtained for annealing temperatures smaller than 180∘C. Therefore, we conclude that the proposed combination of our two optical methods is well suited to determine electrical resistances of organic layers.

The Influence of PEDOT to PSS Ratio on the Optical Properties of PEDOT:PSS Thin Solid Films - Insight from Spectroscopic Ellipsometry

“…It is thus not astonishing that properties of PEDOT:PSS became an object of intense scientific research, e.g. [1][2][3][4][5][6][7][8] and references therein.…”

In-line monitoring and quality control of flexible organic electronic materials

“…Until now, conductivities above 800 S/cm have been reported (Herrmann et al, 2012;Logothetidis & Laskarakis, 2009b;Nardes et al, 2007). Pristine PEDOT:PSS yields a conductivity of below 10 S/cm, however, the addition of solvents (such as ethylene glycol, sorbitol, glycerol, dimethylsulfoxide) and postdeposition processing (e.g., annealing) improves its electrical conductivity.…”

“…PEDOT:PSS consists of a conducting part, PEDOT, a low-molecular weight polymer, which is insoluble and thus difficult to process, and an insulating polymer, PSS, that is a high-molecular weight polymer that gives the desirable flexibility and solubility in water solutions, making the polymer blend easy to process (Herrmann et al, 2012;Logothetidis & Laskarakis, 2009b;Nardes, Kemerink, & Janssen, 2007). One of the most promising materials is poly(3,4-ethylenedioxy-thiophene):poly(styrene-sulfonate) (PEDOT:PSS) that combines metallic-like behavior with sufficient solubility for printing onto large areas.…”

“…The optical response of the PEDOT:PSS includes an absorption in the ViseUV spectral region between 5.3 and 6.4 eV that can be attributed to the pep* transitions of the benzene rings of the PSS part (Herrmann et al, 2012;Logothetidis & Laskarakis, 2009b;Nardes et al, 2007). Also, the absorbance of the more conductive PEDOT part is reported to appear at lower energy values below 1.7 eV (Koidis et al, 2013b;Koidis et al, 2011).…”

“…In addition, the resistivity r and the electrical conductivity s of PEDOT:PSS can be calculated by the combination of the Drude model parameters (the plasma energy u p and Drude broadening G D ) that can be estimated from the analysis procedure of the measured <ε(u)> (Herrmann et al, 2012;Humlicek et al, 1998;Irene & Tompkins, 2005;Laskarakis, Karagiannidis, Georgiou, Nikolaidou, & Logothetidis, 2013). The Lorentz part can describe the electronic transitions at higher energies, whereas the Drude model can successfully describe the metallic-like behavior of PEDOT:PSS at the low-photon energies.…”