title: Tuning of the stability and energy levels of singlet exciton fission relevant excited states of pentacenes by site-specific substitution.
abstract: Pentacene crystals or oligomers undergo efficient singlet exciton fission (SF) after photo-excitation, which is expected to be useful in overcoming the Shockley-Queisser theoretical limit of solar cells. However, pentacenes are extremely unstable in air due to oxidation by oxygen. In this work, we designed a group of pentacene compounds with different substituents at different positions. The energy levels of HOMO and LUMO, which are believed to be closely related to the stability of pentacene, were calculated. The relationship between the molecular structure and the stability was discussed. The driving force for SF was estimated from the difference between the energy of first singlet excited state (E(S1)) and the energy of two triplet excited state (2×E(T1)) following equation E(S1)-2E(T1). Strong electron-withdrawing groups can stabilize pentacene compounds significantly, but induce a decrease on the driving force of SF slightly. Electron-donating groups destabilize the pentacene compounds dramatically and hence the introduction of electron donating groups to pentacene is not recommended. TIPS is an ideal group to improve the stability of pentacene compounds. TIPS does not change the driving force of SF significantly. Sulfur containing groups are also efficient on stabilizing pentacene compounds. These groups increase the driving force of SF at ɑ position, and recued the driving force of SF at other positions. The results of this work provide a theoretical ground for rational design of new SF molecules based on pentacenes.
authors.affiliation: Department of Chemistry, Shandong University, Jinan 250100, China.
authors.forename: Li
authors.initials: L
authors.lastname: Shen
authors.affiliation: Department of Chemistry, Shandong University, Jinan 250100, China.
authors.forename: Yuhan
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Chinese Academy of Sciences, Urumqi 830011, China; Department of Chemistry, Shandong University, Jinan 250100, China. Electronic address: xiyouli@upc.edu.cn.
authors.forename: Xiyou
authors.initials: X
authors.lastname: Li
authors.affiliation: Longkou Entry-exit Inspection and Quarantine Bureau of People's Republic of China, Shandong, China.
authors.forename: Chungang
authors.initials: C
authors.lastname: Li
mesh_terms: D004583:Electrons; D015394:Molecular Structure; D009279:Naphthacenes / Q000737:chemistry*; D009930:Organic Chemicals / Q000737:chemistry; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D011789:Quantum Theory
chemical_list: D009279:Naphthacenes; D009930:Organic Chemicals; C057718:6-(Dimethylamino)-2-((1E,3E)-4-(4-(dimethylamino)phenyl)-1,3-butadien-1-yl)-1-ethylquinolinium perchlorate; C523499:pentacene; D010100:Oxygen
keywords: Electron-donating; Electron-withdrawing; Pentacene; Singlet fission; Stability