## 3 Results and Discussion  
Electrical and Structural Properties of Mesoporous TiO\({}_{2}\) Doped with FK209 Cobalt and Lithium  
The use of lithium TFSI salt (Li\({}^{+}\)) and FK209 cobalt TFSI salt and a mixture of FK209/Li\({}^{+}\) salt as dopant for the M-TiO\({}_{2}\) ETL layer were investigated. The electronic properties of the doped M-TiO\({}_{2}\) were measured using the van der Pauw technique based on four probes hall measurement system. Table 1 illustrates that the conductivity and mobility of the M-TiO\({}_{2}\) doped with FK209 is much higher than the M-TiO\({}_{2}\) doped with Li\({}^{+}\) salt and higher than M-TiO\({}_{2}\) doped with FK209/Li\({}^{+}\) mixture. This is because the M-TiO\({}_{2}\) doped with FK209 has lower surface roughness which leads to denser films improving the conduction path compared to M-TiO\({}_{2}\) doped with FK209/Li\({}^{+}\) mixture. The electrical properties of the M-TiO\({}_{2}\) doped with FK209 or lithium presented in Table 1 were measured on FTO glass substrate. The conductivity and mobility properties of the control undoped M-TiO\({}_{2}\) are \(2.2\times 10^{4}\) [1/\(\Omega\).cm] and \(29.3\) [cm\({}^{2}\)/v.s] respectively [16]. The surface morphology of the M-TiO\({}_{2}\) doped with FK209 and Li\({}^{+}\) were studied using atomic force microscopy (AFM). The AFM images in Figure 1 show that the surface of the M-TiO\({}_{2}\) doped with FK209 cobalt has denser grains structure and minimal surface roughness as compared to the M-TiO\({}_{2}\) doped with FK209/Li\({}^{+}\) mixture salt or doped with Li\({}^{+}\). The \"root mean square\" (RMS) of the surface roughness of the M-TiO\({}_{2}\) layer doped with FK209 shows more homogeneous and smoother surface with an RMS = 16 nm compared to M-TiO\({}_{2}\) doped with Li\({}^{+}\) or doped with FK209/Li\({}^{+}\) which has an RMS value of 25.46 nm and an RMS of 22.75 nm respectively. Figure 1 on the right hand side shows the contact angle measurement of doped and undoped M-TiO\({}_{2}\), and on the left hand side presents the three dimensional AFM imaging for films with the different dopants used and for the undoped M-TiO\({}_{2}\). The x- and y-axes are equal to 1 \(\upmu\)m and the z-axis ranges from \(-\)0.1 to 0.13 \(\upmu\)m. It was found that the surface roughness of the M-TiO\({}_{2}\) doped with cobalt was 16 nm and has the lowest surface roughness compared with lithium doped M-TiO\({}_{2}\) (25.4 nm). This cannot be visualized clearly by just looking at the image only, the Z scale in Figure 1a is 0.08 \(\upmu\)m and in Figure 1b,c is 0.09 \(\upmu\)m. The appearance of the dark and light areas is not necessarily an indication of actual holes in the structure but rather difference in the heights. This was reflected on the size of the perovskite crystal grains as smoother M-TiO\({}_{2}\) surfaces resulted in larger perovskite grain size [9], as shown in Figure 2 histogram. Surface wettability (hydrophilicity) was investigated using the contact angle (\(\theta\)) value between DI water droplet and a surface. The surface is more hydrophilic, if DI water droplet on the surface is more flat with small contact angle value. It can be observed from Figure 1 that the contact angle of the undoped M-TiO\({}_{2}\) control sample is higher than the M-TiO\({}_{2}\) layer treated with other dopants. It is found that doping with lithium or cobalt employed in this study resulted in a reduction in contact angle and has increased surface hydrophilicity compared to pristine sample. There is significant difference in the contact angle of undoped M-TiO\({}_{2}\) (\(\theta\) = 14\({}^{\circ}\)) compared to M-TiO\({}_{2}\) doped with FK209 (\(\theta\) = 4.2\({}^{\circ}\)), an indication of the improved wettability of TiO\({}_{2}\) layer. This could be due to the reduction of the surface roughness of the layer. Hence, by doping the M-TiO\({}_{2}\) with FK209, a more hydrophilic surfaces were achieved.