Photovoltaic Devices Based on Novel Carbon/Thiophene Supramolecular Structures

For verifying the influence of donor-acceptor supramolecules on photovoltaic properties, different hybrids were designed and employed in organic solar cells. In this respect, reduced graphene oxide (rGO) was functionalization with 2-thiophene acetic acid (rGO-f-TAA) and grafted with poly(3-dodecylthiophene) (rGO-g-PDDT) and poly(3-thiophene ethanol) (rGO-g-PTEt) to manipulate orientation of poly(3-hexylthiophene) (P3HT) assemblies. Face-on, edge-on, and flat-on orientations were detected for assembled P3HTs on rGO and its functionalized and grafted derivatives, respectively. Alteration of P3HT orientation from face-on to flat-on enhanced current density (Jsc), fill factor (FF), and power conversion efficiency (PCE) and thus Jsc = 7.11 mA/cm2, FF = 47%, and PCE = 2.14% were acquired. By adding phenyl-C71-butyric acid methyl ester (PC71BM) to active layers composed of pre-designed P3HT/rGO, P3HT/rGO-f-TAA, P3HT/rGO-g-PDDT and P3HT/rGO-g-PTEt hybrids, photovoltaic characteristics further improved, demonstrating that supramolecules appropriately mediated in P3HT:PC71BM solar cells. Phase separation was more intensified in best-performing photovoltaic systems. Larger P3HT crystals assembled onto grafted rGOs (95143 nm) may have acted as convenient templates for the larger and more intensified phase separation in P3HT:PCBM films. The best performances were reached for P3HT:P3HT/rGO-g-PDDT:PCBM (Jsc = 9.45 mA/cm2, FF = 54%, and PCE = 3.16%) and P3HT:P3HT/rGO-g-PTEt:PCBM (Jsc = 9.32 mA/cm2, FF = 53%, and PCE = 3.11%) photovoltaic systems.