Output voltage of multieffect coupled NGs. (a) Voltage signals generated by a pyro-piezo-photovoltaic NG with ITO/BTO/Ag configuration [15
]. Copyright 2019, Royal Society of Chemistry. (b) Voltage of a piezo-tribo-pyro-photovoltaic NG with PZT-FEP/nylon hybrid configuration [45
]. Copyright 2017, Wiley. (c) Voltage produced by a pyro-piezoelectric NG on the basis of Ag/BTO/Ag configuration [46
]. Copyright 2019, Wiley. (d) Output voltage of a thermo-photovoltaic NG with ITO/ZnO/Ag configuration [40
]. Copyright 2019, Wiley.