## 3 Results and Discussion
Nevertheless, the relative change of the permittivity is not greater than 13%, and is without deviation  
Figure 4: Frequency dependence of the (**a**) relative permittivity and (**b**) dielectric losses at different temperatures for the non-bended sample PET/PEDOT:PSS/ZnO/PEDOT:PSS/Au. of the temperature dependence of the permittivity. The stability in the \(\epsilon_{r}\)-\(f\)-\(T\) characteristics is due to the mechanical stability of the structure from using PEDOT:PSS as electrodes. It was proven that the excellent elastic properties of the substrate/polymeric electrode system, and specifically PET/PEDOT:PSS, are responsible for stable contact resistance and dynamic capacitance in the flexible electronic devices, thus leading to stable electrical characteristics at bending [33]. Tan \(\delta\) for the bended samples increased an average of one order of magnitude for the different frequencies and temperatures, showing that the electrical processes revealed in the nanobranched structure are also accomplished by a higher heat loss. In addition, there is a shift in their minimum values to the lower frequencies. After removing the bending force, it was noted that the characteristics restore their initial shape without hysteresis. In general, the dielectric losses for the harvesting device with nanobranched ZnO are smaller than those reported in the literature for devices with high surface-to-volume ratios of the piezoelectric film nanostructure, such as nanowire clusters, for example [34]. This is due to the presence of non-tightly packaged nanoformations, which allow for fluent dipoles orientation and low resistance during polarization. As a result, the generated voltage reached a value more than three times higher than the typical high-density ZnO piezoelectric film's structure, as shown in Figure 6.  
In order to demonstrate the ability of the samples to be used as energy-harvesting devices at low frequencies of mechanical stimulus, the oscillograms of the generated piezoelectric voltage were presented at two frequencies: \(-10\) Hz and \(200\) kHz. They were selected from the frequency range where the dielectric losses are minimal (0.04-0.05 (Figure 6a) and 0.2), or close to maximal (Figure 6b) at cyclic bending conditions and room temperature. The set mechanical loading in this case is \(350\) g force units, and the deflection radius is \(12\) mm. The Y-scale is \(500\) mV/div for each oscillogram. Figure 5: Frequency dependence of the (**a**) relative permittivity and (**b**) dielectric losses at different temperatures for bended sample PET/PEDOT:PSS/ZnO/PEDOT:PSS/Au. Figure 6: Oscillograms of the generated piezoelectric voltage at frequencies, corresponding to the low (**a**) and high (**b**) dielectric losses regions. Thus, in the low frequency region, the open circuit voltage can reach approximately 1 V. In the higher frequencies region, due to the increased dielectric losses and worsening electromechanical coupling, it can reach an average of 300 mV. The harmonic distortions of the signal are due to the rough nature of the ZnO film surface. Although the top casted PEDOT:PSS solution is highly viscous in order to make the ZnO surface smoother and flatter, it seems that still, the ZnO contacts irregularly with the top electrode coatings. For estimation of the flexible microgenerator's stability, two types of tests were performed: a dynamic test at a frequency of bending 10 Hz and a mechanical load of 350 g force units, at which the generated signal is the strongest, and a static test (without cyclic repeating bends). In the first case (Figure 7a), soon after the 10,000 th bend (equivalent to \(\sim\)17 h duration of intensive cyclic bending without interruption), the structure sharply exhibited zero current flow similarly to open circuit behavior. This is probably due to electrode failure caused by microcracks occurring in the electrode films, which deteriorate the charge carriers' path to the electrical poles.