## 3 Results and Discussion
The uncertainty values associated with each thickness (formulation) represent the average roughness (\(R_{avg}\)) acquired from the AFM, and a slight trending toward increasing nominal thickness was observed as the molar ratio was increased, despite the wide variability in \(R_{avg}\), not uncommon for spin-coated perovskite films. The slight increase in the average thickness with increasing concentration may be linked to the associated increase in viscosity since the spin coating parameters remained fixed. The UV-vis optical absorption profiles for all the fabricated films are shown in Figure 4a. For comparison, the absorption profiles of all the MAPbI\({}_{3}\) perovskite films were in agreement with the prior reported studies [41]. Here, it can be seen that the (1.5:1.5) film showed optimal absorption characteristics amongst all the films, which is consistent with its compact morphology, as corroborated through the SEM imaging re \begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{1}{c}{**MAPbI\({}_{3}\)**} & \multirow{2}{*}{**Peak Position (\(\theta\))**} & \multicolumn{1}{c}{**FWHM**} & \multirow{2}{*}{**Crystallite Size (nm)**} \\ \multicolumn{1}{c}{**(MAI:PbI\({}_{2}\))**} & & & \\ \hline
1.0:1.0 & 7.06 & 0.00337 & 43.4 \\ \hline
1.2:1.2 & 7.05 & 0.00330 & 44.2 \\ \hline
1.5:1.5 & 7.06 & 0.00303 & 48.1 \\ \hline
1.6:1.6 & 7.06 & 0.00321 & 45.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Crystalline grain size of perovskite films for all four formulations. Figure 3: Perovskite films on glass substrates with film thickness \(h\) obtained from AFM for the various equimolar concentrations of MAI:PbI\({}_{2}\) with \(R_{avg}\) as uncertainty values for, (**a**) (1.0:1.0): 287 \(\pm\) 97 nm, (**b**) (1.2:1.2): 317 \(\pm\) 72 nm, (**c**) (1.5:1.5): 337 \(\pm\) 58 nm, and (**d**) (1.6:1.6): 346 \(\pm\) 66 nm. sults in Figure 2c. A validation of the slight increase in thickness with an increase in concentration is also evident in the absorption data, where the absorbance increased as the concentration increased, i.e., from the smallest concentration (1.0:1.0) to the highest concentrations, specifically (1.5:1.5) and (1.6:1.6). The absorbance of the (1.5:1.5) and (1.6:1.6) films was almost identical up until about 575 nm, and below 550 nm, the absorbance of the (1.5:1.5) film increased at these shorter wavelengths. This is likely due to the fact that the (1.5:1.5) film depicts a more compact morphology with fewer pinholes compared to all the other film formulations, which may contribute to its slight enhancement in absorbance when compared to the almost equally thick (1.6:1.6) film. The PL emission peak (Figure 4b), for all the fabricated perovskite samples, lies in the vicinity of ~778 nm and aligns well with the prior literature for MAPb\({}_{3}\) films [42]. The lesser PL counts or highest PL quenching for the (1.5:1.5) perovskite formulation on c-TiO\({}_{2}\)/FTO/glass substrates may be likely due to the more efficient charge extraction between the c-TiO\({}_{2}\) and perovskite layer, which further suggests that the (1.5:1.5) film is more suitable for the PSC devices. However, since PL quenching can also arise from non-radiative recombination, steady-state PL, when combined with time-resolved photoluminescence (TRPL), would provide a firmer validation of the efficiency of the charge carrier extraction process, which will be conducted in a future study. PSCs with all four formulations were fabricated based on the n-i-p architecture (Au/Spiro-OMeTAD/MAPbI3/c-TiO\({}_{2}\)/FTO), as shown by the device schematic in Figure 5a, and their recorded current density versus voltage (_I-V_) characteristics are shown in Figure 5b. The (1.5:1.5) PSC exhibited a maximum PCE of 14.56% among all formulations along with an open-circuit voltage _V_OC of ~1.05 V, short-circuit current density _J_SC of ~22.21 mA cm\({}^{-2}\), fill-factor (_FF_) of ~62.58%, series resistance _R_S of ~8.82 \(\Omega\) cm\({}^{2}\), and shunt resistance _R_Sh of ~3.49 k\(\Omega\) cm\({}^{2}\).