Transparent materials with both ionic and electrical conductivity and mixed conducting properties are used in devices which require a membrane with both electrical and protonic conductivity but minimal light absorption– such as some water splitting solar cells. Blending conjugated polymers is one approach to achieve electrical and ionic conductivity; however, polymer membranes formed from blending two polymers often suffer from poor mechanical properties and polymer phase separation.
In this hot paper Paula T. Hammond and co-workers at Massachusetts Institute of Technology, USA, demonstrate that they can tune the ionic conductivity, the electrical, optical, and mechanical properties of PEDOT:sPPO by changing the composition ratio and by DMSO treatment. The polymer thin films become more transparent, smoother, softer, and exhibit higher proton conductivity as the sPPO ratio in PEDOT:sPPO is increased. After DMSO treatment, the polymer electrical conductivity dramatically increased without jeopardizing the protonic conductivity.
Highly transparent mixed electron and proton conducting polymer membranes: Junying Liu, Nicole R. Davis, David S. Liu and Paula T. Hammond, J. Mater. Chem., 2012, DOI: 10.1039/C2JM32296J (Advance Article)