Development of a Triboelectric Nanogenerator for Joining of Silver Nanorods

On account of their excellent properties, 2D nanostructures beyond graphene, such as MoS2, have extensive applications. Given their quantum confinement effects, MoS2 monolayers could efficiently trap electrons as an intermediate layer between friction and electrode in triboelectric nanogenerators (TENGs) and successfully hinder their recombination and air breakdown, increasing their output. With the help of this phenomenon, a TENG called PS+PS/MoS2‐AHSG (PPMA) TENG is fabricated with an open‐circuit voltage of ≈1200 V and a short‐circuit current of 0.74 mA, and a maximum power of 11.27 mW. PPMA TENG consists of transparent polystyrene (PS) and PS/MoS2 as negative contact and storage layers. Also, the positive layer is a novel Alyssum homolocarpum seed gum (AHSG) layer, which is a natural polymer. This TENG could successfully light up 115 commercial light‐emitting diodes. PPMA TENG exhibits exceptional mechanical robustness so that after a decrease in its outputs, heating would activate the self‐healing mechanism, and the surface charge density could reach from 0.428 to 0.874 µC m−2, which is 82% of the initial value. To demonstrate the practical applications of PPMA TENG as a high‐voltage sustainable power source, it is successfully employed to perform a dielectrophoretic assisted welding of silver nanorods.

electron traps and prevent charge loss. It was demonstrated that rGO nanoflakes could suppress the recombination of generated negative with positive charges. The aforementioned TENG exhibited a power density of 6.3 W m −2 which was 30 times greater than TENG without the PI-rGO layer. Aside from rGO, other materials, such as graphene oxide, [14] titania, [15] and MoS 2 , [16] could operate as electron traps. In another research, Wu et al. [16] investigated a TENG with MoS 2 /PI electron trap layer with 25.7 W m −2 , which is 120 times more than that of the device without MoS 2 monolayer. The open-circuit voltage of TENG with MoS 2 was 400 V.
Among nanomaterials, with electron-accepting characteristics, 2D MoS 2 has exceptional properties. [17] MoS 2 is a transition metal dichalcogenide (TMD) having a Mo layer sandwiched between two sulfur layers, typically in a hexagonal configuration. These monolayers consist of three sub-layers (S-Mo-S) held together with van der Waals forces in bulk MoS 2 , which are several orders of magnitude weaker than in-plane covalent bonds. [18,19] Therefore, exfoliation of bulk MoS 2 is a facile approach for producing single-and/or few-layer MoS 2 . [20,21] MoS 2 flakes are semiconductors with a tunable bandgap that ranges from 1.2 eV indirect bandgap at Γ point of the Brillouin zone in bulk to 1.8 eV direct bandgap at K point in single layer form. [22,23] This bandgap tunability is caused by quantum confinement effects leading to alterations in hybridization between p z orbitals of sulfur atoms and d z 2 orbitals of molybdenum near Γ point, which manifests in a downward energy shift at Γ point with thickness reduction or a rise in interlayer separation distance. Ultimately, thinning down the thickness of MoS 2 flakes to monolayer results in an indirect to direct bandgap transition. [24][25][26] High surface-to-volume ratio, flexibility, and chemical stability along with semiconducting properties made 2D MoS 2 ideal for the fabrication of various thin and transparent flexible electronic devices, wearable devices, and body implantation devices, as well as TENGs. [27] Seol et al. [28] investigated triboelectric properties of various layered 2D materials and concluded that MoS 2 exhibited the most tribo-negative properties among MoSe 2 , graphene, graphene oxide, WS 2 , and WSe 2 , and it was located in the triboelectric series between polydimethylsiloxane (PDMS) and polytetrafluoroethylene (PTFE). The superior negative triboelectric charging of MoS 2 was linked to its highly effective work function (4.85 eV). The voltage and current of the fabricated TENG with MoS 2 as negative and Nylon as positive contact material reached 7.48 V and 0.82 µA respectively, with a power density of 36.3 mW m −2 . Several studies have investigated negative contact materials based on MoS 2 in TENGs. [28][29][30][31] Moreover, Wu et al. suggested using MoS 2 as an electron trap material below negative contact material with high efficiency and outstanding outputs. [16] Currently, TENGs have been suggested to be employed in various fields. TENGs' application could be divided into four main categories including blue energy, micro/nano power sources, self-powered sensors, and high voltage power sources. [32] Considering the output characteristics of TENGs, they could act as high-voltage power sources for a variety of novel and stateof-the-art applications. [33] For example, Cha et al. [34] reported a cold-welding method using a non-uniform electric field created by an alternate current (AC) function generator between two electrodes. In this method, the non-uniform electric field would induce dielectrophoresis (DEP) force [35] between gold nanoparticles leading to cold-welding of gold nanoparticles and fabrication of nanoribbons. According to the AC nature of contact-separation TENGs as an alternative to function generators, TENGs could act as the power source for the cold-welding of nanoparticles.
In this work, a novel PS/MoS 2 nanocomposite was employed for both the negative contact layer and electron-accepting layer with a PS and PS/MoS 2 bilayer structure. The structure and thickness of the negative layer were optimized with a new positive contact layer made of Alyssum homolocarpum seed gum (AHSG), which is a natural polymer introduced to prepare the PS+PS/MoS 2 -AHSG (PPMA) TENG and it was subsequently optimized. The prepared TENG was utilized to perform a welding process on silver nanorods (Ag NRs).

Results and Discussion
To investigate the surface morphological features of fabricated layers, scanning electron microscopy (SEM) characterization was performed on AHSG, PS, and PS/MoS 2 layers (Figure 1a-c). It could be inferred that there are no significant surface features in all of the layers. Therefore, surface roughness does not dramatically affect the variations in the output of TENGs, but, these variations are rooted in suitable materials selection and the electron trapping ability of MoS 2 . Figure 1d shows a crosssection view of PS+PS/MoS 2 layers and their corresponding indium tin oxide/polyethylene terephthalate (ITO/PET) substrate. The difference between PS and PS/MoS 2 is obvious due to their dissimilar contrast and also their thickness was 35 and 25 µm, respectively.
Moreover, the UV-vis spectrum of MoS 2 dispersion is presented in Figure 1e. Two A and B peaks at 613 and 675 nm stem from direct-gap transition at the K point of the Brillouin zone, indicating successful exfoliation of MoS 2 and synthesis of monolayers. To further characterize the exfoliated MoS 2 flakes, transmission electron microscopy (TEM) images of the sample were obtained (Figure 1f). This is also another indication of the successful synthesis of monolayer MoS 2 , which has a large surface area and superior electron-trapping properties. The presented flake has a 124 × 70 nm size and approximately an area of 7572 nm.
To evaluate the role of MoS 2 monolayer efficiency as a contact material or as a charge trap TENGs with PS, PS/MoS 2 , PS+PS/ MoS 2 , and PS+PS negative layers were fabricated. In order to compare the fabricated TENGs, their voltage was measured under 8 N force with a 4 Hz frequency. As shown in Figure 2a, the average voltage of PS TENG was 74.20 V, while the average voltage of PS/MoS 2 TENG was 338.89 V. This evidence demonstrates that the MoS 2 as a contact material has a tendency to charge negatively upon contact. This tendency could be attributed to the surface density of states and the effective work function of contact materials. [13,36,37] Since MoS 2 has a higher work function than the tribo-positive material (in this case, PET), charge transfer will occur from the filled electronic states of the tribo-positive material during contact electrification. Therefore, due to the presence of MoS 2 , the effective work function www.advelectronicmat.de difference between triboelectric contact layers was increased and as a result, the amount of created charge on the surface of the PS/MoS 2 layer was higher than that of the PS layer. [13] More importantly, the average voltages of PS+PS TENG and PS+PS/MoS 2 TENG were 52.84 and 615.99 V, respectively. The voltage saw a 12-fold growth once the MoS 2 nanocomposite was incorporated into the TENG. Wu et al. [16] highlighted the existence of electrons in MoS 2 by fabricating a floating-gate metalinsulator-semiconductor (MIS) device and studying its capacitance-voltage curves. The behavior of MoS 2 nanocompositebased MIS was similar to that of a typical p-Si-based MIS device with charge-trapping regions. The presence of such sites could be attributed to the electron-trapping effect of the MoS 2 in the polymeric nanocomposite. It was reported that the captured electrons could occupy both energy states at trap sites on the interface of MoS 2 and the bottom of the conduction band. [16] The probability of electron occupation is greater for energies below the Fermi energy level, due to the Fermi-Dirac distribution. [38] To explore further the influence of MoS 2 concentration on PS+PS/MoS 2 and PS/MoS 2 TENGs, TENGs with various concentrations were fabricated and their voltage was evaluated to optimize the concentration of MoS 2 in nanocomposites. The concentration of MoS 2 dispersion in N-methyl-2-pyrrolidone (NMP) was estimated using the Bear-Lambert method ( Figure S1 (Figure 3). Cui et al. [4] observed the same trend for the electron trap layer, indicating that the majority of the triboelectric charges are stored in the bottom layer. The top layer's thickness varied from 35 to 15 µm and the open-circuit voltage dwindled from 964.15 to 756.32 V ( Figure 3). After selecting the best configuration of negative layers, its application as a single-electrode mode TENG was examined.
A 7 × 3 cm 2 ITO/PET substrate was spin-coated with PS/ MoS 2 then PS and placed on the touchscreen of a smartphone just above the keyboard. Figure 4a shows the output of the setup when typing. The inset picture illustrates the energy harvesting layer on the smartphone screen, indicating the high transparency of the PS+PS/MoS 2 bilayer. To further investigate the transparency of triboelectric layers, UV-vis spectra of had high transparency even the bilayer structure. Following complete negative layer optimization, the concentration of positive AHSG layer was performed and the result is available in Figure S2, Supporting Information, then a TENG composed of  After fabrication, the output of the PPMA TENG was measured under various forces ranging from 2 to 10 N. Under 8 N, the voltage reached its peak value of ≈800 V, which is twice as high as the output under 2 N. By increasing the applied force to 10 N, the output dropped to 400 V (Figure 5a). Subsequently, the frequency response of PPMA TENG was investigated under 1-6 Hz. As demonstrated in Figure 5b, PPMA TENG performed better under 4.5 Hz frequency, with the maximum voltage exceeding 900 V, which is three times higher than the voltage under 1 Hz. This improvement in the performance of PPMA TENG could be associated with a rise in the average velocity of the applied force by increasing the frequency. This tendency, however, is only maintained for frequencies up to 4.5 Hz. Output diminished at frequencies higher than 4.5 Hz. This phenomenon  www.advelectronicmat.de is prevalent in TENGs; at elevated frequencies, the contact cycle is insufficient which means the succeeding cycle initiates before the previous cycle is completed. Therefore, PPMA TENG output at 6 Hz was ≈500 V. To further investigate the performance of PPMA TENG, its output was evaluated under various external loads ranging from 10 3 to 10 10 Ω. Figure 5c represents the current and voltage under multiple loads. Short-circuit condition was established at low loads where the current reached its maximum value of 0.74 mA. Once the external resistance was increased, the voltage was raised, and the current gradually declined until the open-circuit condition was achieved at 632 MΩ and voltage saturated and reached a plateau at ≈1200 V. Figure 5d shows the power and the power density of PPMA TENG, which their maximum value was 11.27 mW and 1.25 mW cm −2 , respectively, at 500 MΩ. According to Figure S3, Supporting Information, a PPMA TENG without the MoS 2 monolayer, but with the same thickness, has open-circuit voltage, short-circuit current, and power of 143 V, 0.13 mA, and 0.12 mW respectively. This is an indication of the extensive effect of MoS 2 as an electron trap in PPMA TENG.
To determine the TENG function for practical applications, it was connected to a conventional full-bridge rectifier. The rectified voltage is displayed in Figure 5e. The rectified output was then used to charge a 1 µF capacitor to 3.3 V in 20 s with the rectified output. The charging of the capacitor is depicted in Figure 5f and the inset displays the charging curve with higher magnification. It could be concluded that a 0.24 µC charge was stored in the capacitor with each contact separation cycle. Additionally, the rectified TENG was connected to 115 commercial blue light-emitting diodes (LEDs) to assess its function under resistive load. PPMA TENG could successfully light up all the LEDs simultaneously (Figure 5g). To further investigate the principle of PPMA TENG, a finite element method using COMSOL Multiphysics was performed and the potential distribution of PPMA TENG was obtained (Figure 5h). The open-circuit voltage of PPMA TENG was calculated to be 1239 V by COMSOL which is only 3% different from the experimental result.
PPMA TENG is a contact-separation mode TENG which is a prominent nanogenerator. The working principle of this TENG is depicted in Figure 6a. Once AHSG as the positive layer is brought into contact with PS as the negative layer by an external force, a charge transfer from the positive to the negative layer occurs, which is due to the overlap of wave functions and different electronic structures. This is called contact www.advelectronicmat.de electrification and until the layers are pressed together and the electrostatic equilibrium is maintained, no potential difference is observed (state I). By removing the force, layers separate and the charges on positive and negative layers are no longer in equilibrium (state II). Therefore, these electrostatic surface charges induce their counterpart on the back electrodes, which is called electrostatic induction. Connecting electrodes to an external circuit, a charge transfer from the bottom electrode to the top electrode could be observed to maintain another equilibrium and it is continued until the layers reach their maximum distance. While the layers reach their initial position, the electrodes saturate; hence there is no current between them (state III). Provided that TENG was subjected to a load again, as the layers move toward each other, electrons flow back from the top electrode to the bottom electrode (state IV). [39,40] By continuing this contact and separation process, an AC signal is produced, which could be employed for various applications.
In PPMA TENG, PS/MoS 2 layer under the negative contact layer acts as a negative charge storage layer. Figure 6b compares the charge trapping mechanism in a TENG with and without PS/MoS 2 . After contact, both positive and negative triboelectric charges accumulated on the surface of contact materials. Without PS/MoS 2 , if the contact materials separate, an electric field stemming from the induced positive charges on the bottom electrode attracts negative charges on the surface of PS. This electric field could be calculated using the following equation where σ T (x,t) is the surface electrostatic charge, ε T is the total permittivity of the combined PS+PS/MoS 2 layer, and ε 0 is vacuum permittivity. Furthermore, since these negative charges are stored in shallow traps, they drift toward the electrode under the influence of an electric field in dielectrics and combine with positive charges on the electrode. Inserting the PS/MoS 2 layer between the electrode and PS creates abundant deep trap sites, which could effectively trap negative charges and retard the drift process. Consequently, the induced charges in the bottom electrode rise, and this means the performance of the TENG improves.
To investigate the electron trap sites in PS/MoS 2 , a Mott-Schottky plot of PS and PS/MoS 2 was obtained (Figure 7) using where C is space charge capacitance, A is the area of the film, e is electron charge (1.6 × 10 −19 C), ε is the relative permittivity of film, ε 0 is vacuum permittivity (8.85 × 10 −23 F m −1 ), N A is carrier density, V FB is flat-band potential, k is Boltzmann constant (1.38 × 10 −23 J K −1 ), and T is temperature. The temperature term is generally small and can be neglected. . The carrier density of PS/MoS 2 film was estimated at 1.9 × 10 25 cm −3 using the above method. It is clear that the n-type behavior of PS/MoS 2 comes from the intrinsic n-type properties of MoS 2 , which largely depends on interactions between MoS 2 and its surrounding. [41] Having the lowest formation energy, sulfur vacancies could be the origin of the n-type conductivity of MoS 2 . [42] Rudimentary density function theory (DFT) calculations have demonstrated that sulfur vacancies introduce localized donor states in the bandgap, resulting in the generation of unpaired electrons into the lattice and thus n-type doping of the MoS 2 . [43] On the other hand, extensive DFT calculations indicated that the most abundant native defect (sulfur vacancy) in MoS 2 is either in a neutral or negative charge state. Therefore, being a deep acceptor, it cannot be the cause of the observed n-type properties. [44] In fact, the origin of the intrinsic semiconducting behavior of MoS 2 still remains unclear. [45] The inherent defects, such as sulfur vacancies, may not be efficient n-type dopants in MoS 2 , although they could still act as a deep electron trap center, [46] suppressing the immigration of electrons toward electrodes in PS/MoS 2 . It is worth mentioning that PS has also shown electron trapping ability due to the discontinuity of energy caused by benzene rings. [47,11] Therefore, the superior electron trapping behavior of the PS/MoS 2 composite could be due to the synergic effects of both MoS 2 and PS.
Durability is a vital property concerning the practical application of TENGs. PPMA TENG durability was assessed during 10 000 contact separation cycles. The open-circuit voltage was monitored at 5-min intervals during the first 1808 s and as it is shown in Figure 8a, no reduction was observed in the first 1808 s, but after 10 000 cycles, the average open circuit plummeted to 484 V. Nevertheless, after holding the PS+PS/MoS 2 layer in 70 °C for 3 h, an increase in the output of PPMA TENG was observed and the average open-circuit voltage reached 987.77 V. It was calculated that prior to the durability test, the surface charge of PPMA TENG was 1.067 µC m −2 whereas, after 10 000 cycles, it was declined to 0.428 µC m −2 . However, after annealing the PS+PS/MoS 2 , the surface charge raised to 0.874 µC m −2 which was 82% of the initial value. This enhancement in the output www.advelectronicmat.de of PPMA TENG could be assigned to the self-healing of PS. It was reported by McGarel et al. [48] that surface cracks in PS films could be eliminated by heating. The primary mechanism for self-healing stimulated by heating is diffusion and randomization of minor polymer chains. [49][50][51] The PS surface before and after healing is shown in Figure 8c,d. Figure 8c depicts the surface of PS after 10 000 contact-separation cycles with a crack in the middle. After the healing process, there were no signs of cracks on the surface of PS meaning that the healing process was carried out successfully. After fully characterizing PPMA TENG, its application as a power source for a joining process will be discussed next.
Considering the AC nature of TENGs output, they could be employed to perform a nanoparticle joining process reported by Cha et al. [34] If the suspension of Ag NRs is subjected to a non-uniform electric field, the generated DEP force instigates the joining process of Ag NRs. Figure 9a depicts the FE-SEM images of Ag NRs prior to the joining process. The average width of synthesized Ag NRs was 112 ± 29 nm and their aspect ratio was estimated to be ≈9. Figure 9b demonstrates two NRs joined together by PPMA TENG. This assembly of NRs and their welding was also observed in other studies. [52] The schematic of the joining process setup is presented in Figure 9c. The assembled NRs not only attached but also welded together. Ag NRs on the Kapton were subjected to DEP, Lennard-Jones potential, and Coulomb forces. It was observed that DEP accumulates NRs near the tip of another NR to assist the joining process and for a cylindrical rod parallel to an electric field, it could be estimated using Equation (3) [53] where r is the radius, L is the length of NRs, Re[ f CM ] is the real part of the Clausius-Mossotti factor, E rms is the root-meansquare electric field, and ε m is the real part of the complex permittivity of the surrounding medium of NRs. Obviously, electrophoresis force depends on the gradient of the electric field. To obtain a qualitative distribution of the electric field, COMSOL was employed and the result of modeling is depicted in Figure 9d when the voltage is 1200 V and the frequency is 4.5 Hz. This demonstrated that the electric field distribution in the space was equal and homogenous in a constant time.
The DEP force could successfully gather the NRs, but it is not sufficient to weld two NRs. In other words, NRs move in the direction of the electric field, and this transport due to DEP force increases the density of Ag NRs in the suitable position for joining. The joining occurs only when the concentration of Ag NRs accumulated at the tip of another Ag NR is sufficiently high to sustain the joining. Under the electric field, Ag NRs are charged with opposite polarity and the Coulomb force attracts the NRs and induces the welding while the Lennard-Jones force from the substrate account for the alignment of Ag NRs, consequently the tip of Ag NRs attach together leading to a tip-to-tip cold-welding. [34]

Conclusion
To conclude, PPMA TENG was fabricated using a straightforward spin-coating method in which a transparent bilayer commercial blue LEDs were successfully illuminated, also a 1 µF capacitor was charged with the PPMA TENG which with each contact-separation cycle 0.24 µC was stored in the capacitor. This TENG manifested excellent durability before 10 000 cycles and after that, because of the self-healing properties of the negative layer, the output increases again given that the TENG was heated. It was proved that PPMA TENG could be successfully employed to weld Ag NRs together with the help of the AC nature of TENGs output.

Experimental Section
Materials: NMP, molybdenum(IV) sulfide (MoS 2 ) powder (<2 µm, 98%), polystyrene (pellets, average M w = 350 000), polyvinylpyrrolidone (PVP) (M w = 40 000), silver nitrate (AgNO 3 ), Iron(III) chloride hexahydrate (FeCl 3 .6H 2 O), and ethylene glycol were obtained from Sigma-Aldrich Co. and used without further purification. ITO/PET substrates (Nanogostar Sepahan Co., Iran) with a thickness of 175 µm and resistance of 15 ohm sq −1 were used as electrodes for TENG fabrication. Alyssum homolocarpum seeds were purchased from a local market. Cellulose tape (Top tape Co., China) was employed to adhere wires to the back of ITO electrodes. Ethylene-vinyl acetate (EVA) foam obtained from a local store was used as a protective layer around fabricated TENGs. Kapton sheet (Nanobazar Co., Iran) was utilized as an insulator for the coldwelding process. Figure 9. Welding of Ag NRs. FE-SEM images of Ag NRs a) before, b) after welding, and c) welding process schematic. d) Electric field simulation between two electrodes during the joining process.

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Preparation of MoS 2 Nanosheets: MoS 2 nanosheets were obtained by a modified liquid-phase exfoliation method. [54] After sonication, the prepared dispersion was centrifuged at 45 000 rpm for 45 min to remove the un-exfoliated MoS 2 flakes. The supernatant on top was carefully collected to avoid the un-exfoliated precipitates at the bottom of the falcon centrifuge tube. Finally, a dispersion with light yellow color was obtained and stored for further use. Figure 10a demonstrates a schematic of MoS 2 nanosheet preparation.
Fabrication of TENGs: 1.602 gr PS was solved in 3.642 gr NMP and then mixed with 0.878 gr MoS 2 /NMP dispersion on a stirrer for 3 h at 60 °C. This solution was spin-coated on 3 × 3 cm 2 ITO/PET substrates with different speeds and a PS solution was also spin-coated on top of the PS/MoS 2 layer with several speeds to create the negative contact layer of TENG. All of the spin-coated films were dried at 60 °C for 3 h. This bi-layer structure formed the tribo-negative layer of TENG. Presumably, MoS 2 acted as a trap for electrons, and the PS/MoS 2 with a thickness of 25 µm was an electron storage layer. Copper wires were attached at the back of ITO/PET layers and the electrodes were adhered to a strip of EVA foam using cellulose tape. Finally, two ends of the EVA foam were attached using double-sided tape and two arcshaped supports were created to maintain a 1 cm gap between positive and negative layers. This TENG was named PS+PS/MoS 2 . In order to compare the electron storage ability of PS/MoS 2 nanocomposite with its contact electrification ability, a TENG named PS/MoS 2 consist of a single layer nanocomposite of PS/MoS 2 as negative contact layer and AHSG as positive contact layer with the same as-mentioned method was fabricated. Also, a TENG with a single PS layer as the negative layer and another TENG with a bilayer both made of PS was fabricated with the same method. Those two TENGs were labeled as PS and PS+PS, respectively. Figure 10b shows the fabrication process of these TENGs.
For fabrication of the tribo-positive layer, 0.166 gr AHSG was added to 5 mL deionized water and the dispersions were spin-coated on top of another ITO/PET substrate. The tribo-positive layer was dried at room temperature for 1 day. AHSG was extracted based on a method described by Koocheki et al. [55] Then a TENG consisting of PS+PS/ MoS 2 -AHSG called PPMA TENG was fabricated with the same method described above.

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Characterization of TENG Layers: SEM (Philips XL30 SERIES) was used to characterize the morphology of triboelectric layers. Before the imaging process, the samples were coated with a thin layer of gold. The synthesized MoS 2 monolayers were characterized by TEM (Zeiss-EM10C) operating at 100 kV. Also to determine the UV-vis spectra of MoS 2 monolayers, PS, PS/MoS 2 , and PS layers, a UV-vis spectrophotometer (Metash-Model UV-6100 Series) was employed. The Mott-Schottky test was performed within the range from −1.5 to 0.5 V versus Ag/AgCl reference electrode a solution of 0.5 m Na 2 SO 4 (pH = 7) was utilized as an inert electrolyte under a frequency of 1 kHz.
Characterization of TENG Device: The current was measured with a custom-built current preamplifier (CNI570). [56] The voltage was measured with digital oscilloscopes (MEGATEK-DSO5070 and Keithley 2450 sourcemeter). Also, the power and power density of TENG were evaluated using voltage and current. Furthermore, TENG was directly connected to LEDs to examine the operation of the TENG in practical conditions. In all measurements, the electrode attached to the PS+PS/ MoS 2 was connected to the ground terminal of the oscilloscope, while the electrode attached to the AHSG layer was connected to the positive terminal. COMSOL Multiphysics software was used to perform finite element analysis. To calculate the potential distribution of PPMA TENG in the open-circuit condition, the electrostatic module was used. Moreover, the potential difference between electrodes was reported.

Supporting Information
Supporting Information is available from the Wiley Online Library or from the author.