  The thin film configuration presents obvious practical advantages over the 1D
implementation in energy harvesting systems such as easily manufacturing and
processing and long lasting and stable devices. However, most of the ZnO-based
piezoelectric nanogenerators (PENGs) reported so far relay in the exploitation
of single-crystalline ZnO nanowires because their self-orientation in the
c-axis and ability to accommodate long deformations resulting in a high
piezoelectric performance. Herein, we show an innovative approach aiming to
produce PENGs by combining polycrystalline ZnO layers fabricated at room
temperature by plasma assisted deposition with supported small-molecule organic
nanowires (ONWs) acting as 1D scaffold. The resulting hybrid nanostructure is
formed by a single-crystalline organic nanowire conformally surrounded by a
three dimensional (3D) ZnO shell that combines the mechanical properties of the
organic core with the piezoelectric response of the ZnO layer. In a loop
forward towards the integration of multiple functions within a single wire, we
have also developed ONW@Au@ZnO nanowires including a gold shell acting as inner
nanoscopic electrode. Thus, we have built and compare thin films and 3D
core@shell ONW@ZnO and ONW@Au@ZnO PENGs showing output piezo-voltages up to 170
mV. The synergistic combination of functionalities in the ONW@Au@ZnO devices
promotes an enhanced performance generating piezo-currents almost twenty times
larger than the ONW@ZnO nanowires and superior to the thin film nanogenerators
for equivalent and higher thicknesses.
