## 3 Results
### Efficiency of DSSCs  
The photovoltaic (PV) performance of the fabricated DSSC devices with the ITO film is evaluated. Figure 16a shows an image of the fabricated ITO-nanorod-based DSSC sample experimentally used in this work. As can be seen in Figure 16b, the ITO-nanorod film is an electron-collecting layer. TiO\({}_{2}\) nanoparticles of 15-20 nm size are interconnected in three dimensions on the ITO-nanorod layer. For this, many dye molecules injected into the TiO\({}_{2}\) nanoparticle layer will adhere to the large surface of nanoparticles, enabling efficient harvesting. In this work, the TiO\({}_{2}\) paste was provided by the sol-gel combustion method with a thickness of 10 \(\upmu\)m, which was coated on glass by the screen-printing technique. In this part, the short-circuit current was received without external potential. The efficiency of DSSC devices was calculated concerning the solar spectrum by calibrating a 1000-light drive lamp with direct sunlight. The efficiency of photon-to-current conversion was indicated by the range of 450-700 nm when measuring the light intensity. The photocurrent (I) and photovoltage (V) of the ITO-nanorod-based DSSC devices were carefully measured. In the measurement, an ITO-nanorod film with an active area of 0.2 cm\({}^{2}\) was annealed at 250\({}^{\circ}\)C through simulated sunlight at AM-1.5 generated by a 200 W solar simulator. J\({}_{\text{sc}}\) is the total photocurrent density or the current obtained under short-circuit conditions divided by the cell area. The Voc is the open circuit voltage, and FF is the  
Figure 15: Electrical properties on ITO-nanorod film treated with oxygen plasma compared with ASD film using four-point probe technique. fill factor related to the series resistance for practical solar cells. In addition, electrical impedance measurements were performed via V\({}_{\text{oc}}\) under no-current conditions. In the PV performance, the DSSCs structure is defined as follows: ITO-nanorod treated with oxygen plasma used as a working electrode, deposited with TiO\({}_{2}\), N 719 dye used as the photosensitizer, I\({}^{-}\)/I\({}^{-}\)\({}_{3}\) used as an electrolyte [45], and platinum (Pt) used as the counter electrode. Thus, the assembly structure of the DSSC device is glass-deposited ITO-nanorod/TiO\({}_{2}\)/(I\({}^{-}\)/I\({}^{-}\)\({}_{3}\))/Pt, respectively [46; 47; 48; 49]. Figure 17 illustrates the I-V characterization on ITO-nanorod film applied with DSSC devices. The overall \(\upeta\) of DSSCs, meaning the percentage of solar energy that shines on a photovoltaic device, which is converted into electricity, was tested by J\({}_{\text{sc}}\), V\({}_{\text{oc}}\), and FF, which are calculated by Equation (5) [50], as shown in Table 1.  
\[\upeta(\%)=\frac{\text{J}_{\text{sc}}\times\text{V}_{\text{oc}}\times\text{ FF}}{\text{P}_{\text{in}}} \tag{6}\]  
Figure 16: Images of the ITO-nanorod based on DSSC device created with DSSC cell size 2.5 cm \(\times\) 2.5 cm: (**a**) assemble cells of DSSC device; (**b**) model of cell structural. Figure 17: I–V characteristics of DSSCs on ITO-nanorod treated with oxygen plasma of varying gas contents at 20, 40, 60, 80, and 100 sccm provided via bias-magnetron RF sputtering process. Figure 18 shows the overall efficiency of DSSC devices, comparing ASD film and ITO-nanorod film treated with oxygen plasma in different conditions of gas flow rates. The trend illustrates that when the oxygen gas flow rate is increased, the \(\eta\) of the photovoltaic improves. Compared with ASD film, the samples treated with oxygen plasma exhibited higher efficiency, especially at an oxygen gas flow rate of 100 sccm, showing the highest efficiency of 9.5%. It produces higher energy oxygen plasma with more oxygen gas ions. When falling to ITO-nanorod substrates, the substrate surface is modified by enhancing the roughness of the ITO-nanorod (working electrode) to allow greater dye absorption.