# Organic Nanostructured Materials for Sustainable Application in Next Generation Solar Cells
## 2 Types of Organic Solar Cells
### Small-Molecule OPV Cells  
Small-molecule OPVs feature well-defined molecular architectures that give outstanding mechanical stability and charge carrier flexibility, allowing for greater efficiency gains [47]. Most small molecule OPVs are based on electron-rich thiophene units, supporting the importance of this heterocyclic core in materials science. [PERSON] and [PERSON] [48] conducted a study in 2018 to investigate the impact of nanomolecular architectures of electron donors on interfacial arrangements and intermolecular charge-transfer (CT) processes for small-molecule OPVs by means of multiscale theoretical simulations. They synthesized three oligothiophene [49] nanomaterial derivatives namely, D-\(\pi\)-A-\(\pi\)-D, \(\tau\)-A-D- A-\(\pi\) and A-\(\pi\)-D-\(\pi\)-A which served as donors (D) in combination through a pie-bond (\(\pi\)) with the fullerene acceptor (A) (6,6)-phenyl C71-butyric acid methyl ester (PC\(\gamma_{1}\)BM). To acquire the mesoscopic morphologies of the two colleagues' materials, the two colleagues used the melt-quenched [50] approach to perform atomistic molecular dynamics (MD) simulations, which were successfully implemented to elucidate the interfacial geometries for the donor/acceptor blends of each derivative named above. They were able to attain PCEs of 7-9% while assembling their devices based on the three mixtures, which is not as awful for fullerene-based devices. Their findings also revealed that regardless of the varying push-pull configurations of electron donors, HOMO levels tend to be more concentrated on the material's core unit. Non-fullerene equivalents have made greater development in recent years, inspired by the success of fullerene-based small molecule OPVs. DSSCs have been developed throughout the last three decades, according to the latest data of verified efficiency tests from the National Renewable Energy Laboratory (NREL), however, their efficiency has achieved saturation of about 12%. (See Figure 5). [PERSON] et al. [3] ascribed this to the use of nanostructured photoanode components notably mesoporous Titanium dioxide (TiO2) with complex core-shell nanocomposite and face-oriented nanocrystal designs, as well as counter electrode adjustment. The OPVs have a shorter background than the DSSCs, but they show promise because their efficiency has increased by nearly 17%. (See Figure 5). Nanomaterials may play a significant part in OPVsin a variety of ways. Surface states passivation and morphological modification, organic layer protection, energy barrier reduction, charge transport selection, and optical spacer are all possible with nanomaterial at the interfaces. All of these characteristics will help to reduce energy loss at the OPV cell's interface. Finally, the PSCs have a higher efficiency than most commercial polycrystalline silicon photovoltaic cells (Figure 5), which is around 25%. Nanomaterials are commonly employed in PSC electrodes, charge transport layers, and perovskite photoactive layers, much as they are in OPVs. The performance of PSCs has been improved using the knowledge learned from OPVs and DSSCs. To explore the potentiality of non-fullerene-based nanomaterial as next generation for sustainable organic photovoltaics, [PERSON] and colleagues [46] lately in 2019 designed and synthesized two nanomaterial non-fuleferere acceptors, 3.9-Bis(2-methylene- ((3-,1,1-dicyanomethylene)-6/7-chloro)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno [2,3-d-2',3-d'-d']-s-indaceno[1,2-b-5,6-b']dithiophene (IT-2 Cl) and 3,9-bis(2-methylene-((3-(1,1-dicyanomethylene)-6,7-dichloro)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2',3-d'-d']-s-indaceno[1,2-b:5,6-b']dithiophene (IT-4 Cl) from a typical synthetic route of 3,9-bis(2-methylene-((3-(1,1-dicyanomethylene)-6,7-difluoro)-indanone))-5,5,11,11-tetrakis (4-hexylphenyl)-dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene (IT-4F) as shown in Figure 6A below.