- Multiphonon relaxation slows singlet fission in crystalline hexacene
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Singlet fission, the conversion of a singlet excitation into two triplet excitations, is a viable route to improved solar-cell efficiency. Despite active efforts to understand the singlet fission mechanism, which would aid in the rational design of new materials, a comprehensive understanding of mechanistic principles is still lacking. Here, we present the first study of singlet fission in crystalline hexacene which, together with tetracene and pentacene, enables the elucidation of mechanistic trends. We characterize the static and transient optical absorption and combine our findings with a theoretical analysis of the relevant electronic couplings and rates. We find a singlet fission time scale of 530 fs, which is orders of magnitude faster than tetracene (10-100 ps) but significantly slower than pentacene (80-110 fs). We interpret this increased time scale as a multiphonon relaxation effect originating from a large exothermicity and present a microscopic theory that quantitatively reproduces the rates in the acene family.
- Busby, Erik,Berkelbach, Timothy C.,Kumar, Bharat,Chernikov, Alexey,Zhong, Yu,Hlaing, Htay,Zhu,Heinz, Tony F.,Hybertsen, Mark S.,Sfeir, Matthew Y.,Reichman, David R.,Nuckolls, Colin,Yaffe, Omer
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- Synthesis and physical properties of brominated hexacene and hole-transfer properties of thin-film transistors
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A halide-substituted higher acene, 2-bromohexacene, and its precursor with a carbonyl bridge moiety were synthesized. The precursor was synthesized through 7 steps in a total yield of 2.5%. The structure of precursor and thermally converted 2-bromohexacene were characterized by solid state NMR, IR, and absorption spectra, as well as by DFT computation analysis. It exhibited high stability in the solid state over 3 months, therefore can be utilized in the fabrication of opto-electronic devices. The organic thin-film transistors (OFETs) were fabricated by using 2-bromohexacene and parent hexacene through vaccum deposition method. The best film mobility of 2-bromohexacene was observed at 0.83 cm2 V-1 s-1 with an on/off ratio of 5.0 × 104 and a threshold of -52 V, while the best film mobility of hexacene was observed at 0.076 cm2 V-1 s-1 with an on/off ratio of 2.4 × 102 and a threshold of -21 V. AFM measurement of 2-bromohexacene showed smooth film formation. The averaged mobility of 2-bromohexacene is 8 fold higher than the non-substituted hexacene.
- Watanabe, Motonori,Miyazaki, Takaaki,Matsushima, Toshinori,Matsuda, Junko,Chein, Ching-Ting,Shibahara, Masahiko,Adachi, Chihaya,Sun, Shih-Sheng,Chow, Tahsin J.,Ishihara, Tatsumi
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- HEXACENE DERIVATIVE, METHOD FOR FORMING HEXACENE, METHOD FOR FORMING HEXACENE CRYSTAL, PROCESS FOR MAKING ORGANIC SEMICONDUCTOR DEVICE, AND ORGANIC SEMICONDUCTOR DEVICE
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A hexacene derivative is described, being expressed by formula (1): wherein X1-X6 denote the presence or absence of a carbonyl bridge [—C(═O)—], with a proviso that at least one of X1-X6 is a carbonyl bridge while any six-member ring absent of a carbonyl bridge is aromatic. A method for forming hexacene is also described, including: thermally treating the hexacene derivative to expel volatile units of CO from the hexacene derivative.
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- Synthesis, stability, and photochemistry of pentacene, hexacene, and heptacene: A matrix isolation study
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The photochemical bisdecarbonylation of bridged α-diketones (Strating-Zwanenburg reaction) to give the oligoacenes pentacene (2), hexacene (3), and heptacene (4) is investigated in solid inert gas matrices at cryogenic temperatures. The photodecomposition
- Mondal, Rajib,Toenshoff, Christina,Khon, Dmitriy,Neckers, Douglas C.,Bettinger, Holger F.
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experimental part
p. 14281 - 14289
(2010/02/16)
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