Fig. 3: Effects of field emission on output characteristics of CS-TENG from contact to separate state.

a Test circuit to maximize the output energy of CS–TENG on the load. A diode is parallel connected with the CS-TENG to achieve charge reset. b, c Output charge of CS–TENG with different load resistance. d Output current of CS–TENG with different load resistance. e Normalized charge of CS–TENG with different load resistances. Theoretically, it is predicted that surface charges keep stable at different load resistances. Data are presented as mean values ± SD, n = 3 independent experiments. f V–Q curves of CS–TENG with different load resistance. g Electric circuit of CS–TENG charging a capacitor and the corresponding equivalent circuit model. From the perspective of electric circuit, the CS–TENG in separate condition is a dielectric capacitor (C_D) and a gas capacitor (C_g) connected in series. C_f is an external fixed capacitor. h Schematic diagram shows that the V–Q curve of CS–TENG for charging different capacitors. A series of charge (Q₁, Q₁ and Q₃) and voltage (V₁, V₁ and V₃) can be obtained by changing the external fixed capacitor (C_f). By linearly connecting these charge and voltage points in the V–Q figure, the V–Q curve of CS–TENG can be obtained theoretically. i The actual obtained V–Q curve for charging different capacitors w/ breakdown. The breakdown effect limits the achievable maximum output voltage. The output voltage curve of CS–TENG for charging the capacitor of j 220 pF and k 22 pF. l Experimental V–Q curves of CS–TENG with different dielectric thickness. The gray dashed line shows the possible predicted V–Q curve w/o breakdown. Data are presented as mean values ± SD, n = 5 independent measurements. Source data are provided as a Source data file.