Effect of annealing on the electrical properties and morphology of a conducting polymer used as an anode in organic light‐emitting devices

Abstract

The surface sheet resistance of conducting films of glycerol‐doped poly(3,4‐ethylenedioxy‐thiophene)–poly(styrene sulfonate) is largely dependent on the annealing temperature. The presence of free glycerol in insufficiently baked films, as indicated by infrared spectra and thermogravimetric analysis, results in conducting polymer films with poor morphology and low electrical conductivity. The device performance of organic light‐emitting diodes using this modified poly(3,4‐ethylenedioxy‐thiophene)–poly(styrene sulfonate) as an anode is also greatly affected by the baking conditions of the conducting films. The maximum light output, current density, and luminous power efficiency are observed from devices using anodes baked at a high temperature close to the boiling point of glycerol. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2522–2528, 2003

A comparative study of electrode effects on the electrical and luminescent characteristics of Alq3/TPD OLED: Improvements due to conductive polymer (PEDOT) anode

“…Theoretical discussion of the injection efficiency shows that organic-organic heterostructure barriers at the organic-organic interface is a significant limitation to charge injection [15], and it is reasonable to conclude that charge injection is improved by relocating the barrier to the more conductive PEDOT layer. In addition, the spun-on PEDOT film (as measured with an AFM) is slightly rougher, with a typical roughness of 5 nm [16], compared to 3 nm for the ITO surface directly. Both the optimized band offsets [17] and the morphology have been previously shown to improve carrier injection and device performance.…”

Improving the performance of ITO thin films by coating PEDOT:PSS

“…6,7 OPVs or OLEDs with a PEDOT:PSS layer on top of an ITO anode have longer lifetime and higher photovoltaic performance than those using ITO anode alone. 8 The improvement in device stability can be attributed to the ability of the polymer coating to clean the anode surface that substantially slows down device degradation. The photovoltaic performance improved because the conducting polymer may produce a smaller energy barrier that lowers the turn-on voltage of the electronic device.…”

Modification of conductive polymer PEDOT:PSS layer by SWCNT

“…PEDOT:PSS offers many advantages over other conducting polymers because of its ease of processability, commercial availability, high optical transparency in visible light, good mechanical strength, superb thermal stability and excellent atmospheric stability. High quality films can be easily formed on various substrates by conventional solution processing techniques such as spin-coating techniques [1,2,3,4].…”

“…PEDOT:PSS is generally used as antistatic coatings and as a hole injection layer in organic devices due to high work function, high hole affinity, and good transparency [2,3,5,6,7]. However, pristine PEDOT:PSS has a low conductivity (generally below 10 S/cm) [6].…”