Electron Acceptability of Cyclopenta-Fused Polycyclic Aromatic Hydrocarbons: Effect of One Electron

To accurately predict the electron acceptability of cyclopenta-fused polycyclic aromatic hydrocarbons (CP-PAHs), we evaluated the performance of six functionals, B3LYP, CAM-B3LYP, HSEH1PBE, PBE, TPSS, and HCTH, using eight CP-PAHs. The results show that B3LYP is the best to obtain the energy of the highest occupied molecular orbital (HOMO), the energy of the lowest unoccupied molecular orbital (LUMO), and the HOMO-LUMO energy gap of CP-PAHs with a mean absolute error (MAE) of 0.14 eV. The current study also demonstrates that calculations must be carried out for the anion of the corresponding CP-PAH in order to predict LUMO energy of an electron acceptor. Time-dependent CAM-B3LYP with the B3LYP optimized geometry predicts the absorption spectra of CP-PAHs most accurately with a MAE of 29 nm. The results from B3LYP and time-dependent CAM-B3LYP calculations coupled with the new practice in calculating LUMO energy presented in this work show that six of the eight CP-PAHs can accept electrons from the donor material poly(3-hexylthiophene)(P3HT), thus indicating they can be used as electron acceptors of P3HT. Moreover, three pairs of CP-PAHs were identified for their use as highly efficient organic solar cell materials through construction of a P3HT-acceptor1-acceptor2 architecture.