Schottky DC generators from polypyrrole nanocomposites of N-type semiconductor metal oxides and the multiple device connection effect

Abstract

Schottky DC generators based on conducting polymers and low work function metals can convert small mechanical energy into DC power, showing potential for self-powered electronics. However, research on Schottky DC generators is still in its early stages, and many issues must be clarified. This study examines two important aspects of polypyrrole-based Schottky DC generators: (1) the effect of three inorganic n-type semiconductors (SnO₂, WO₃, and CeO₂) and (2) multiple device connections on the mechanical-to-electrical energy conversion performance. All the metal oxides showed enhancement in the current outputs but to a different degree. When the metal oxide content in polypyrrole (PPy) was ∼7 wt%, the SnO₂-involved devices had a short-circuit current of 340.78 μA (working area of 1.33 cm²) and power density of 48.85 μW cm⁻², which were 28 times and 132 times higher when compared with those of the device made of pure PPy (12.18 μA, 0.37 μW cm⁻²). Under a similar condition, the WO₃-involved devices showed a short-circuit current and power density of 308.67 μA and 44.01 μW cm⁻² and the CeO_2-involved devices showed a short-circuit current and power density of 45.97 μA and 6.32 μW cm⁻². The outputs showed an increasing and decreasing trend with increasing the metal oxide content. The maximum current outputs occurred at different metal oxide contents, 6.73 wt%, 6.90 wt%, and 11.76 wt% for the SnO₂-, WO₃-, and CeO₂-involved devices. These improvements were explained by formation of micro p–n junctions between the p-type PPy and n-type metal oxide nanoparticles, which reduced the internal resistance and Schottky barrier height. We further showed that the multidevice connection profile greatly impacted the overall output of multiple device assemblies, especially when some local devices were deactivated during the energy conversion process. The all-parallel connection had minimal loss of electrical energy. We hope that these novel understandings will contribute to developing high-performance Schottky DC generators.