Electron blocking layer-based interfacial design for highly-enhanced triboelectric nanogenerators

The key to enhance the output power from triboelectric nanogenerators (TENGs) is to control the surface charge density of tribo-materials. In this study, we introduce an electron blocking layer (EBL) between a negative tribo-material and an electrode to dramatically enhance the output power of TENGs. For the first time, we suggest that the tribo-potential can be significantly reduced by the presence of interfacial electrons; electrostatically induced positive charges at the interface beneath a negative tribo-material can be screened out by the electrons, thereby decreasing the surface charge density. By employing an EBL between a negative tribo-material and an electrode, we can maintain a high surface charge density at the surface of the negative tribo-material. Furthermore, an EBL with high permittivity can enhance the polarization of the tribo-material, resulting in an improved surface charge density. As a proof of concept, polydimethylsiloxane (PDMS) and aluminum (Al) are used as a negative tribo-material and an electrode, respectively. A TiO_x EBL is then deposited in between these materials by radio frequency (RF) sputtering. Due to the coupling effects of the electron blocking and enhanced polarization, the output peak power from the TENG with a TiO_x EBL reaches approximately 2.5 mW at 3 Hz and 5 N, which is 25 times larger than that of a TENG without an EBL. To understand the improved behavior of the TENG with a TiO_x EBL, we investigate the correlations between the output behavior of the TENG and the physical properties of the surface/interface of TiO_x and PDMS (e.g., the surface potential, dielectric properties, and electronic structures). We expect that our results can provide a novel design way to significantly improve the output performance of TENGs.