Yingtao Xie

Surface patterning of PEDOT: PSS by photolithography for organic electronic devices

Along with the development of organic electronics, conductive polymer of PEDOT:PSS has been attracting more and more attention because they possess various novel electrical, optical, and mechanical properties, which render them useful in modern organic optoelectronic devices. Due to its organic nature, it is lightweight and can be fabricated into flexible devices. For better device processing and integrating, it is essential to tune their surface morphologies, and photolithography is the best choice at present. In this paper, current PEDOT:PSS patterning approaches using photolithography are reviewed, and some of our works are also briefly introduced. Appropriate photolithographic patterning process for PEDOT:PSS will enable its application in future organic electronics.

Two Photolithographic Patterning Schemes for PEDOT:PSS and Their Applications in Organic Light-Emitting Diodes

Poly(3,4-ethylenedioxythio-phene):poly(styrenesulfonate) (PEDOT:PSS) is a promising conductive polymer in future flexible applications. To apply PEDOT:PSS into organic electronic devices, patterning processes are essential. Here, two photolithographic patterning schemes are introduced, namely fluorinated materials and silver interlayers. With hydrofluoroethers (HFEs) solvents and fluorinated photoresist, PEDOT:PSS can be patterned down to micro scales. Using a silver thin film to protect PEDOT:PSS surface, traditional photolithographic materials can be applied for PEDOT:PSS patterning. These two patterning processes do not obviously influence the electrical characteristics of PEDOT:PSS, and patterned conductive PEDOT:PSS is successfully applied to organic light-emitting diodes (OLEDs) as anodes. These patterning schemes can easily be used on large substrates, and high-resolution flexible OLED strips are also demonstrated. These results imply that the proposed PEDOT:PSS patterning schemes here have great potential to be employed in organic electronic devices.

Aluminum-Modified Molybdenum Trioxide for Electron Injection in Inverted Organic Light-Emitting Diodes

Electron injection using ambient stable electrodes is essential for organic light-emitting diodes (OLEDs), particularly for the bottom electrode of the inverted OLEDs. Here, a metal-oxide-based highly transparent electron injection layer (EIL) is proposed. This metal-oxide-based EIL consists of thin layer of aluminum (Al)-modified molybdenum trioxide (MoO3). It is demonstrated that the surface of the MoO3 layer can be chemically reduced by a very thin overlayer of Al (1 nm), resulting in a lower effective surface work function as well as introducing a number of gap states in the reduced molybdenum oxide layer. With this surface Al-doped MoO3 EIL, efficient inverted OLEDs are demonstrated over typical conductive electrodes such as indium tin oxide (ITO) and poly(3,4-ethylenedioxythio-phene): poly(styrenesulfonate) (PEDOT:PSS).

High-Performance Solution-Processed Amorphous InGaZnO Thin Film Transistors with a Metal–Organic Decomposition Method

A facile solution process was introduced for the preparation of IGZO thin films via a metal–organic decomposition (MOD) method. The IGZO ink was synthesized by mixing the solutions of gallium acetylacetonate [Ga(C5H7O2)3], zinc acetylacetonate hydrate [Zn(C5H7O2)2·xH2O] dissolved in ethanol, and indium acetylacetonate [In(C5H7O2)3] dissolved in tetrahydrofuran (THF). The deposited films by spin-coating were annealed at moderate process temperature (≤500°C). The relationship between device performance and postannealing temperature was studied. The result demonstrated that mobility of IGZO TFT increased as the annealing temperature increased. Based on the analysis of O 1s statement, the annealing temperature can influence the number of oxygen vacancy to further affect the carrier centration. In addition, the IGZO TFT devices with various Ga molar ratios were compared to demonstrate the influence of the Ga addition. The result demonstrated that the saturated mobilities ( ) decreased and shifted to positive voltage as the Ga molar ratio was increased. It is likely that Ga can offer stronger chemical bonds between metal and oxygen that reduced the concentration of free carriers and thus help reducing . As a result, the optimized performance of IGZO TFT with the mobility of 3.4 cm2V−1s−1 showed the MOD process was a promising approach.