Peculiar optical transition of Davydov excitons in pi-conjugated co-oligomer crystals

• Project/Area Number: 21740223
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Single-year Grants
• Research Field: Condensed matter physics I
• Research Institution: Shizuoka University
• Principal Investigator: BANDO Kazuki Shizuoka University, 理学部, 講師 (50344867)
• Project Period (FY): 2009 – 2010
• Project Status: Completed (Fiscal Year 2010)
• Budget Amount: ¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000); Fiscal Year 2010: ¥2,080,000 (Direct Cost: ¥1,600,000、Indirect Cost: ¥480,000); Fiscal Year 2009: ¥2,340,000 (Direct Cost: ¥1,800,000、Indirect Cost: ¥540,000)
• Keywords: π共役系 / 有機半導体 / コオリゴマー / H会合体 / ダビドフ励起子 / ポラリトン

Research Abstract

Intrinsic optical transitions of upper Davydov excitons in thiophene/phenylene co-oligomer (TPCO) crystals were investigated. Lower Davydov excitons are either optically allowed or forbidden depending on the number of thiophene rings constituting the TPCOs. On the other hand, upper Davydov excitons lying at higher energies have fairly large oscillator strength in ac planes. Since the TPCO molecules are orientated nearly parallel to each other like H aggregates, the upper Davydov excitons show large absorbance compared to the lower Davydov excitons. The transition selection rules are dominated by the arrangements of the molecular transition dipole moments in the respective crystals.