# Organic Nanostructured Materials for Sustainable Application in Next Generation Solar Cells
## 2 Types of Organic Solar Cells
### Polymer-Based OPV Cells  
To investigate the performance of as-synthesized nanomaterial, PolyI(2,6-(4,8-bis(5- (2-ethylhexyl-3-fluoro)thiophen-2-yl)-benzo[1,2-b4,5-b']dithiophene))-alt-(5,5-(1',3'-di-2-thienyl-5',7'-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c']dithiophene-4,8-dione)] (PBDB-T) was employed as a donor to fabricate an OPV device for each of the two acceptors and the OPV device delivered PCE of 14.18% and 13.45% for ITIC-2 Cl and ITIC-4 Cl acceptor, respectively. Figure 5: Summary of the new-generation solar cells presenting their historically developed efficiency (adapted from reference [3] NREL efficiency table). The improved performances of the two single-junction devices, due to the variation in wavelengths for the two acceptors is shown in Table 1.  
To further improve the performance of non-fullerene-based OPVs [PERSON] et al. (2018) developed a copolymer donor, Poly[(2,6-(4,8-bis(5-(2-ethylhexyll-3-fluoro)thiophen-2-yl)-benzo1[1,2-b-4,5-b']thiophene))-alt-5,5'-(5,8-bis(4-(2-butyloctyl)thiophen-2-yl)dithiene) [3',2',3',4',2',3',5',6]benzoyl[1,2-c][1,2,5]thiadiazole) (D18) using a fused-ring acceptor unit, dithieno[3',2',3',4',2',3',5',6]benzo[1,2-c][1,2,5]thiadiazole (DTBT) that has a larger molecular plane [52] and thus, gifted D18 a higher hole mobility. When blended with BTP-4F acceptor, the device demonstrated a PCE of 18.22%, which is the highest efficiency for organic solar cells to date. The second class of OPVs which are conjugated polymer-based OPVs, on the other hand, have also gotten a lot of attention from researchers because of their benefits over silicon-based solar cells, they possess medium or low band-gap; with high carrier mobility and matched energy levels with good solubility. Same as their counterparts, polymer-based OPVs are also divided into two well-known subclasses namely, fullerene and nonfullerene-based polymers [53]. [PERSON] et al. (2018). have recently reported a non-fullerene chlorinated low band-gap nanomaterial acceptor 2,2'-((2Z,2'Z)-((12,13-bis(2-ethylhexyll)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazol[3,4-e]thieno[2\",3\",4',5]thieno[2',3',4',5]pyridrolo[3,2-g]thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis(5,6-dichloro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (BIT-4 CI) [55] where the halogen atoms of the fluorinated non-fullerene acceptor 2,2'-((2Z,2'Z)-((12,13-bis(2-ethylhexyll)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazol[3,4-e]thieno[2',3',4,5]pyrrole[3,2-g]thieno[2',3',4,5]thieno indole-2,10-diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1 \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Type of Material** & \(\mathbf{\lambda_{\text{max}}}\) **(nm)** & **Eg (eV)** & **HOMO (eV)** & **LUMO (eV)** & **J\({}_{\text{ac}}\) (mA/cm2)** & **V\({}_{\text{OC}}\) (V)** & **FF** & **PCE (\%)** \\ \hline IT-2 CI & 720 & 1.69 & \(-\)5.68 & \(-\)3.99 & 22.03 & 0.842 & 0.764 & 14.18 \\ IT-4 CI & 746 & 1.66 & \(-\)5.75 & \(-\)4.09 & 22.67 & 0.790 & 0.752 & 13.45 \\ BTP-4F & 732 & 1.41 & \(-\)5.60 & \(-\)3.55 & 24.9 & 0.834 & 0.753 & 15.3 \\ BTP-4 CI & 746 & 1.40 & \(-\)5.65 & \(-\)3.63 & 25.4 & 0.867 & 0.750 & 16.5 \\ D18 & 625 & 1.98 & \(-\)5.51 & \(-\)2.77 & 27.70 & 0.859 & 0.766 & 18.22 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Photovoltaic performance of small-molecule non-fullerene-based acceptors. Figure 6: Formation of non-fullerene precursors (**A**) the synthesis of ITIC-2 CI and ITIC-4 CI (**B**) chemical structures of ITIC-2 CI and ITIC-4 CI acceptors (**C**) (Reproduced from Reference [46] with permission, copyright 2018 WILY-VCH Verlag GmbH and Co. KGaA, Weinheim, Germany). -diylidene))dimalononitrile (BTP-4F) [56] were replaced with chlorine atoms.