Highly Conductive PEDOT:PSS Films with 1,3‐Dimethyl‐2‐Imidazolidinone as Transparent Electrodes for Organic Light‐Emitting Diodes

Abstract

PSS films with the new solvent of DMI can be a promising transparent electrode for low-cost, efficient ITO-free white OLEDs.

Rising advancements in the application of PEDOT:PSS as a prosperous transparent and flexible electrode material for solution-processed organic electronics

“…Pre-treatment methods involve the simple addition of polar, protic, and aprotic organic solvents miscible with water, such as N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), and ethylene glycol (EG) [32,33,[35][36][37], or of organic compounds that get dissolved in water, such as sorbitol [33,38,39], as well as the incorporation of low-viscosity and transparent ionic liquids like 1-ethyl-3-methylimidazolium tetracyanoborate (EMIM BTI) [16,29] and ionic/non-ionic surfactants like cetrimonium bromide (CTAB), sodium dodecyl sulphate (SDS), and polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ethers (Triton X-100) into the aqueous dispersion of PEDOT:PSS [11,40]. The addition of pre-treatment agents (dopants) into the polymer solution will substantially affect the electrical conductivity, transmittance, and morphology of the formed films.…”

“…For this purpose, a number of post-treatment methods have been developed and investigated, which can lead either to doping or de-doping of the polymer films. These post-deposition approaches imply treating the deposited polymer films with various organic and inorganic substances representing a diverse set of compounds, from the simplest alcohol methanol (MeOH) to more complex chemicals like imidazoles [11,47,48], phenol, and other polar organic solvents, or with water co-solvents with high boiling points, such as DMSO, EG, DEG, TRIEG, ethanol (EtOH), isopropyl alcohol, tertrahydrofuran (THF), and acetone, as well as with different salts [27,37,49,50] and acids [51]. While these methods appear to be simple solvent treatments of the films, there are notable differences in their procedures.…”

“…The approaches for improving the conductivity of PEDOT:PSS can be categorized into two groups: the pre-and post-treatment methods [11,12,15,16]. In this section, these methods will be comprehensively examined.…”

“…Among the conductive polymers, poly(3,4-ethylene dioxythiophene) polystyrene sulfonate (PEDOT:PSS) stands out as the most successful and widely studied, which has also been practically and commercially realized [11][12][13]. This prosperous conductive polymer is a mixture of two polymer ionomers, positively charged PEDOT and negatively charged sulfonated polystyrene (PSS), where PSS acts as a template polymer and surfactant [13].…”

Polythiophene coated poly(methyl methacrylate) sheet as a new candidate for flexible organic electrode applications

“…Notwithstanding excellent electrical conductivity and transparency of ITO layer, some inherent drawbacks of ITO are high price and temperature of manufacturing, rareness of indium, brittleness of ITO layer and increase in electrical resistance in large areas. Hence, the future of flexible electronics seeks for any commodity substitution for ITO in many different routes [4][5][6]. Moreover, in organic light emitting diodes (OLEDs) the large mismatch (~ 1.2 eV) between work function of ITO (anode) and the typical highest occupied molecular orbital (HOMO) of active polymer/organic molecule prohibits surmounting the barrier of hole transfer from ITO [7].…”