Highly Soluble Benzo[ghi]perylenetriimide Derivatives: Stable and Air‐Insensitive Electron Acceptors for Artificial Photosynthesis

Abstract

A series of new benzo[ghi]perylenetriimide (BPTI) derivatives has been synthesized and characterized. These remarkably soluble BPTI derivatives show strong optical absorption in the range of λ=300–500 nm and have a high triplet-state energy of 1.67 eV. A cyanophenyl substituent renders BPTI such a strong electron acceptor (Ered=−0.11 V vs. the normal hydrogen electrode) that electron-trapping reactions with O2 and H2O do not occur. The BPTI radical anion on a fluorine-doped tin oxide|TiO2 electrode is persistent up to tens of seconds (t1/2=39 s) in air-saturated buffer solution. As a result of favorable packing, theoretical electron mobilities (10−2∼10−1 cm2 V−1 s−1) are high and similar to the experimental values observed for perylene diimide and C60 derivatives. Our studies show the potential of the cyanophenyl-modified BPTI compounds as electron acceptors in devices for artificial photosynthesis in water splitting that are also very promising nonfullerene electron-transport materials for organic solar cells.

The Twisted Benzo[ghi]‐Perylenetriimide Dimer as a 3D Electron Acceptor for Fullerene‐Free Organic Photovoltaics

“…Nevertheless, the molecular orbital representation of t‐BPTI in Figure still clearly shows that the HOMO and LUMO are delocalized over the whole t‐BPTI molecule. Thus, the calculated internal reorganization energy ( λ in ) of 127 meV of t‐BPTI is almost half of the value of the BPTI monomer ( λ in =247 meV) . This λ in of t‐BPTI is smaller even than that of PC 61 BM ( λ in =149 meV) at the same level calculation.…”

“…Based on Marcus theory, low internal reorganization energy leads to a low activation barrier and efficient charge separation and charge transport, desirable properties for high‐performance optoelectronic materials . Moreover, the calculated T 1 energy of t‐BPTI is still as high as 1.69 eV when using TD‐DFT at the B3LYP/6‐31G(d) level . We also note that the energy difference between the LUMO and LUMO+1 decreases from 455 meV for BPTI to 9 meV for t‐BPTI (Table S1 in the Supporting Information).…”

“…The synthetic routes to t‐BPTIs are shown in Figure . First, the PDIs with various α‐branched alkyl side chains were obtained in high yield according to the known literature methods . The benzo[ ghi ]‐perylenediimide monoanhydride compounds (BPDIs) could be synthesized in satisfactory yield by Diels–Alder reaction on the PDI scaffold.…”

“…N 1 , N 2 ‐Bis(3‐pentyl)‐perylene‐3,4,9,10‐tetracarboxylic diimide (PDI‐1), N 1 , N 2 ‐bis(4‐heptyl)‐perylene‐3,4,9,10‐tetracarboxylic diimide (PDI‐2), and N 1 , N 2 ‐bis(6‐undecyl)‐perylene‐3,4,9,10‐tetracarboxylic diimide (PDI‐3) were synthesized according to the literature methods …”

“…In contrast to fullerene system, the triplet formation of fullerene is thermodynamically inhibited owing to their higher triplet excited state energies such as PC 61 BM ([6,6]‐phenyl‐C 61 ‐butyric acid methyl ester; E (T 1 )=1.50 eV) . In the rylene imide dye family, particularly, benzo[ ghi ]‐perylenetriimide (BPTI) shows a remarkably high triplet energy level of 1.69 eV . Thus, addressing the issue of triplet state formation through a charge recombination pathway for the loss mechanism in organic photovoltaic cells, BPTI shows its potential as an ideal building block for the novel nonfullerene acceptor design.…”