High output power density owing to enhanced charge transfer in ZnO-based triboelectric nanogenerator

We have fabricated triboelectric nanogenerarators (TENGs) using ZnO and polydimethylsiloxane (PDMS) in which ZnO growth temperature was varied in the range from 450 degrees Ct 750 degrees C. The output voltage/current of TENGs increases with increase of ZnO growth temperature up to 600 degrees C and then decreases with further increase of growth temperature up to 750 degrees C. TENG fabricated with ZnO grown at 600 degrees C exhibits maximum electrical output with peak to peak voltage of -210 V, current -95 mu A and power density -8.8 mW/cm2 upon application of a periodic force of -30 N @ 6 Hz, which is higher than the power densities reported till date in the case of ZnO-based TENGs. This enhanced output power density can be mainly attributed to the large effective work function difference obtained between ZnO and PDMS. Electrical, photoluminescence and ultra-violet photoelectron spectroscopy measurements clearly suggest the dominant role of electron transport in the charge transfer between ZnO and PDMS. Practical applications of TENGs have been demonstrated by powering 38 LEDs and a stopwatch display. This study not only deepens the understanding of contact electrification between ZnO and PDMS, but opens up the immense potential of ZnO-based TENGs for possible vibration energy harvesting applications.