  Piezoelectric energy harvester scavenges mechanical vibrations and generates
electricity. Researchers have strived to optimize the electromechanical
structures and to design necessary external power management circuits, aiming
to deliver high power and rectified outputs ready for serving as batteries.
Complex deformation of the mechanical structure results in charges with
opposite polarities appearing on same surface, leading to current loss in the
attached metal electrode. External power management circuits such as rectifiers
comprise diodes that consume power and have undesirable forward bias. To
address the above issues, we devise a novel integrated piezoelectric energy
harvesting device that is structured by stacking a layer of quantum dots (QDs)
and a layer of piezoelectric material. We find that the QD can rectify
electrical charges generated from the piezoelectric material because of its
adaptable conductance to the electrochemical potentials of both sides of the
QDs layer, so that electrical current causing energy loss on the same surface
of the piezoelectric material can be minimized. The QDs layer has the potential
to replace external rectification circuits providing a much more compact and
less power-consumption solution.
