Fig. 3: Mechanism analysis of the HEEG.
a The built-in electric field distribution under no-bias condition: the inset is a magnified view of the built-in electric field direction near the junction. b Concentration distribution of H+ under no-bias condition: H+ is transferred to the CNT side under the action of the built-in electric field. c OH− concentration distribution under no bias condition: OH− is transferred to the vicinity of the bottom electrode under the action of the built-in electric field. d, e I-V sweeping curves for device in high and low RH condition, which effectively demonstrate the ion-diode characteristics for unidirectional electrical conduction. f, g Surface Zeta potential of CNT film and AAO membrane in different pH condition before and after O-plasma treating, respectively, verifying effective surface modification. h Result of device’s VOC, ISC for four different plasma treating methods, and the HEEG shows the best performance after both membrane material being treated with oxygen plasma.
