ZnO/In/ZnO tri-layer thin films were designed and fabricated by RF sputtering on copolymer substrate. Under an electrical current, the thermoelectric effect of direct current (DC) reduced the electrical resistance and improved the crystallization and Raman properties. Also, indium atoms had migrated into the ZnO matrix and a diffusion layer in the ZnO/In interface had grown. The electrical current induced temperature is $140C and the copolymer substrate suffers no damage and so can be applied to the low temperature optoelectronic devices.