The present disclosure relates to a piezoelectric sensor. The piezoelectric sensor includes a polymer layer, a first metal layer, and a second metal layer. The polymer layer includes pyrolytic polyacrylonitrile. The first metal layer is located on a surface of the polymer layer. The first metal layer includes a first work function. The second metal layer is located on another surface of the polymer layer and includes a second work function different from the first work function. The present disclosure also relates to a method for making the piezoelectric sensor.