A Comparative Study on Electrical and Mechanical Behavior of Indium Tin Oxide and Poly (3, 4-Ethylenedioxythiophene) Thin Films Under Tensile Loads

This paper focuses on the performance of conductive polymer and conducting transparent conductive oxide coated on flexible substrate under tensile loads. Poly (3, 4-ethylenedioxythiophene) (PEDOT) thin films with two different resistances (i.e., 150 and 225 Ω/sq) and indium tin oxide (ITO) thin films with another two different resistances (i.e., 60 and 200 Ω/sq) were used in the experiment. All films were coated on polyethylene terephthalate. A mechanical stretching device was used to stretch all sheets up to 12% of the original length. The considered stretching speeds in terms of strain rate were 0.01, 0.1, and 1 min^-1. Two types of cracks were noticed after stretching of the ITO sheet. The first type was noticed at 6% strain level initiated and propagated perpendicularly to the direction of the load toward the edges of the sample, whereas the second type was noticed at 9% strain level initiated from different points on the first type of cracks and propagated perpendicularly with them. No clear cracks or deformation was seen on the surface of PEDOT after stretching. The percentage change in electrical resistance (PCER) with strain was investigated under three different strain rates, and it was noticeable that PCER increases with strain for both PEDOT and ITO sheets. However, the increase was huge in the case of ITO. Strain and initial sheet resistance were significant factors in terms of affecting the PCER for ITO films under stretching, and all of strain, strain rate, and initial sheet resistance were significant factors in terms of affecting PCER for PEDOT films under stretching according to the analysis of variance study. As a final conclusion from this paper, the electrical performance of PEDOT films is greatly better than that of ITO films under stretching.