## 3 Results and Discussion
On the other hand, for the (1.6:1.6), (1.2:1.2) and (1.0:1.0) formulations, PCE values of ~12.25%, 10.98%, and 9.32% were measured, respectively. The photovoltaic parameters for all PSCs are summarized in Table 2. While there is scope to improve these parameters further, the PCE trend: (1.5:1.5) > (1.6:1.6) > (1.2:1.2) > (1.0:1.0), lies in good agreement with the absorption and PL spectra. The recombination losses for the fabricated PSCs were examined by recording the light intensity-dependent _I-V_ Characteristics. Typically, the _J_SC of the devices follows a power-law relationship with the incident light intensity \(I\) such that, _J_SC \(\propto\)_I\({}^{\alpha}\), where \(\alpha\) is extracted from the slope of the log-log _J_SC versus \(I\) plot, as shown in Figure 6a, and it represents the extent of bimolecular recombination [43; 44]. Usually, \(\alpha\) close to unity indicates  
Figure 4: (**a**) The UV–vis spectra gathered for MAPbI3 perovskite films synthesized on c-TiO\({}_{2}\)/FTO/glass substrates. (**b**) The PL spectra of the perovskite films fabricated on c-TiO\({}_{2}\)/FTO/glass substrates, showing the maximum PL quenching for the (1.5:1.5) formulation, with the peaks largely centered around 778 nm. the presence of weak bimolecular recombination. The \(\alpha\) value for the PSCs were extracted as follows: \(\alpha\) = 0.965 (1.5:1.5) \(>\) 0.950 (1.6:1.6) \(>\) 0.917 (1.2:1.2) \(>\) 0.910 (1.0:1.0). Thus, these data indicate the presence of minimal bimolecular recombination in the (1.5:1.5) PSC. Meanwhile, information about the trap-assisted recombination losses can be obtained from the dependence of the \(V_{\text{OC}}\) and \(I\), according to the following relation, where \(V_{\text{OC}}\)\(\propto\)\(\frac{nRT}{q}\ln(I)\). Here, \(n\) is a coefficient, \(k\) is the Boltzmann constant, \(T\) is the temperature in Kelvin, and \(q\) is the elementary charge. The value of the coefficient \(n\) usually ranges between 1 and 2, where an \(n\)-1 indicates the absence of trap-assisted recombination, while \(n\) \(>\) 1 suggests the presence of trap-assisted recombination [12; 45]. From the fit in Figure 6b, the value of \(n\) in the devices was deduced to be: \(n\) = 1.57 (1.5:1.5) \(<\) 1.63 (1.6:1.6) \(<\) 1.78 (1.2:1.2) \(<\) 1.87 (1.0:1.0), which indicates that the (1.5:1.5) PSC has the least presence of trap-assisted recombination. Overall, both studies shown in Figure 6a,b suggest minimal bimolecular and trap-assisted recombination occurring in the (1.5:1.5) PSC, which also corroborates its higher PCE performance amongst all four formulations. Moreover, the continuous evolution of photovoltaic parameters for (1.5:1.5) PSC with time up to 10 h were monitored while keeping the device at its maximum power point, as shown by the data in Figure 7b. The relative humidity (RH) and ambient temperature during the experiment were noted to be \(\sim\)60% and \(\sim\)29 \({}^{\circ}\)C, respectively. It can be seen that the (1.5:1.5) PSC retained \(\sim\)90% of its initial \(V_{\text{OC}}\) and \(FF\) after 10 h of continuous tracking, but the \(J_{\text{SC}}\) and PCE decreased to \(\sim\)70% and \(\sim\)60%, respectively, of their initial values for the same duration. There might be a number of possible reasons for the \(J_{\text{SC}}\) loss attributed to photo-oxidization, or degradation of the charge extraction layers, or their degraded interfaces with the perovskite reducing the charge extraction efficiency [46; 47], which will be examined further in future work.