High conductivity PEDOT:PSS through laser micro-annealing: mechanisms and application

Conductive polymers represent the next generation of soft, flexible electronics. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is among the most widely used of these, despite having a relatively low conductivity when deposited in the standard form with no additional chemical dopants. This is often mitigated through chemical doping, but this is associated with changes in processing easy, mechanical stability, or compatibility. This paper reports a laser micro-annealing process for PEDOT:PSS, including process optimisation, investigation of the underlying mechanism, and application in organic electronics. The laser micro-annealing increases the material conductivity from 1 S cm(-1) to around 360 S cm(-1) without any additive or post-deposition chemical treatments. This process is used, along with a laser ablation step, to fabricate organic electrochemical transistors (OECTs). These show comparable performance to material fabricated with common additives, while allowing rapid production of myriad devices. The additive and photolithography free processes enables simple fabrication of devices without the processing complications introduced by the use of additional chemicals. Following process optimisation, detailed study of the material properties suggests the dominant mechanism for this conductivity enhancement is the agglomeration of PEDOT cores within the film, facilitated by the moderate local heating action of the laser.