## 3 Results and Discussion
### Electrochemical Properties of H3T-4-Fop
Significantly, without any additives or promotors in the active layer, the FF of the fabricated BHJ-OSCs shows relatively a high value which credits to a suitable morphology and high charge carrier mobility [46]. However, the fabricated BHJ-OSCs with H3T-4-FOP:PC\({}_{61}\)BM (1:1, _w/w_) and H3T-4-FOP: PC\({}_{61}\)BM (1:3, _w/w_) demonstrate lower photovoltaic parameters, as summarized in Table 2. For the H3T-4-FOP: PC\({}_{61}\)BM (1:1, _w/w_) thin film, it is expected that the creation of small barriers at the interfaces between the donor and acceptor units during the fabrication of BHJ-OSCs might be responsible for the occurrence of the high recombination of exciton, which resulted in a low FF [47]. The obtained photovoltaic parameters were compared with the existing research [48; 49; 50; 51], as demonstrated in Table 3.  
Figure 4: (a) Cyclic voltammogram (CV) and (b) 3D structure of H3T-4-FOP SOM. The network of the donor-acceptor interface of an active layer affects the charge separation and extraction efficiency [52], thus, the morphological features of the blend thin films are studied by atomic force microscopy (AFM). The height and 3D images of H3T-4-FOP: PC\({}_{61}\)BM blend films are shown in Figure 6a-f. AFM images clearly indicate the good miscibility of the donor and acceptor moieties. A relatively high mean-square roughness (Rrms) of \(\sim\)8.03 nm is observed in H3T-4-FOP: PC\({}_{61}\)BM (1:1, _w/w_) ratio, as seen in Figure 6a,b, whereas a uniform morphology with an Rrms value of \(\sim\)4.77 nm is observed for the H3T-4-FOP: PC\({}_{61}\)BM (1:2, _w/w_) blend thin film which favors the nanoscale phase separation and efficient exciton dissociation and, thus, attributes to relatively higher Jsc, Voc, and device performance values based on the H3T-4-FOP: PC\({}_{61}\)BM (1:2, _w/w_) active layer. Overall, under optimized conditions, the blend thin film of H3T-4-FOP: PC\({}_{61}\)BM (1:2, _w/w_) demonstrates fine and evenly distributed domains with a continuous interpenetrating network without the existence of large aggregates. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**H3T-4-FOP: PC\({}_{61}\)BM** & **V\({}_{\text{oc}}\) (V)** & **J\({}_{\text{sc}}\) (mA/cm\({}^{2}\))** & **FF (\%)** & **PCE (\%)** \\ \hline
1:1 (_w/w_) & 0.772 & 10.22 & 41 & 3.21 \\
1:2 (_w/w_) & 0.782 & 11.18 & 50 & 4.38 \\
1:3 (_w/w_) & 0.782 & 9.83 & 51 & 3.91 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Photovoltaic parameters of the fabricated BHJ-OSCs devices with H3T-4-FOP:PC\({}_{61}\)BM active layer. Figure 5: (**a**) Energy level diagram and (**b**) J-V curve of fabricated bulk heterojunction organic solar cells (BHJ-OSCs) with the active layer of H3T-4-FOP: PC\({}_{61}\)BM at various ratios (1:1 _w/w_, 1:2 _w/w_, and 1:3 _w/w_). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Organic Chromophores** & **V\({}_{\text{oc}}\) (V)** & **J\({}_{\text{sc}}\) (mA/cm\({}^{2}\))** & **FF (\%)** & **PCE (\%)** & **Reference** \\ \hline RTh-NR:PC\({}_{61}\)BM & 0.59 & 8.70 & 32 & 1.65 & 34 \\ RT-BSe-F:PC\({}_{60}\)BM & 0.71 & 12.56 & 42 & 3.75 & 35 \\ OMe-BF1:TC\({}_{61}\)BM & 0.69 & 8.71 & 58 & 3.53 & 48 \\ DCAE7T:F1:PC\({}_{61}\)BM & 0.83 & 5.55 & 50 & 2.26 & 49 \\ DFP-BT-TPA:PC\({}_{71}\)BM & 0.90 & 6.12 & 39 & 2.17 & 50 \\ PBDTFT-ttTP:PC\({}_{71}\)BM & 0.79 & 8.57 & 48 & 3.27 & 51 \\ H3T-4-FOP:PC\({}_{61}\)BM (1:1, _w/w_) & 0.772 & 10.22 & 41 & 3.21 & This work \\ H3T-4-FOP:PC\({}_{61}\)BM (1:2, _w/w_) & 0.782 & 11.18 & 50 & 4.38 & This work \\ H3T-4-FOP:PC\({}_{61}\)BM (1:3, _w/w_) & 0.782 & 9.83 & 51 & 3.91 & This work \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Comparative study of fabricated BHJ-OSCs with different organic chromophores and H3T-4-FOP.