[18a-P05-1~32] 12.3 Functional Materials and Novel Devices

English Presentation

[18a-P05-3] Transient Spectroscopy Study of Thiophene/Phenylene Co-oligomer Nanocrystals

〇(D)Andi Marwanti Panre¹, Hitoshi Mizuno^1,2, Tomomi Jinjyo¹, Garrek Stemo¹, Hiroyuki Katsuki¹ (1.NAIST, 2.Toyama Pref. Univ.)

Keywords:

Excited-state dynamics,Thiophene/Phenylene Co-oligomer (TPCO) Nanocrystals,Photophysical properties

The photophysical properties of a 5,5’-bis(4’-cyanobiphenyl-4-yl)-2,2’-bithiophene (BP2T-CN) nanocrystal are investigated through transient absorption and steady-state spectra. Transient absorption spectroscopy directly visualizes the transition from a continuum of electronic states to discrete energy levels as nanocrystal size decreases [1]. Our investigation highlights the influence of nanocrystal size on photoluminescence (PL) and absorption spectra, as illustrated in Fig.1 (a), elucidating the significant impact of surface and quantum effects on optical properties [2]. Specifically, NCs #1, NCs #2, and NCs #3 correspond to nanocrystals with average sizes of 550 nm, 260 nm, and 86 nm, respectively. The 0-1 emission bands labelled with closed circles blue-shifted with decreasing nanocrystal size. Transient decay curve of 260 nm BP2T-CN amorphous film and BP2T-CN nanocrystals with an average size of 550 nm are shown in Fig. 1(b) and 1(c). The decay curves are well fitted with three-term exponential decay functions. In amorphous materials, the decay constants with 2.1 ps, 13.6 ps, and 48.5 ps are considered to be complex carrier recombination influenced by numerous defects and traps due to structural disorder. In contrast, the nanocrystalline sample, with an average size of 550 nm, shows fast initial decay (0.6 ps and 2.3 ps) due to rapid surface recombination from a high surface-to-volume ratio, while the slower decay (75 ps) indicates quantum effects and core carrier recombination [3,4]. In the presentation, we will report the results of transient absorption spectral measurements using smaller nanocrystal sizes.