https://scholars.lib.ntu.edu.tw/handle/123456789/581003
標題: | Thickness-Dependent Exciton Dynamics in Thermally Evaporated Rubrene Thin Films | 作者: | Chen C.-H Sher P.-H Chen C.-P Choi W.-K Bardeen C.J Chiu T.-L Wang J.-K JIUN-HAW LEE WING-KIT CHOI |
關鍵字: | Activation energy; Excitons; Film growth; Light absorption; Microcrystals; Red Shift; Singlet fission; Temperature distribution; Thick films; Absorption and photoluminescence; Molecular packings; Relaxation channels; Rubrene thin films; Temperature dependence; Temperature dependent; Thermal annealing treatment; Time-resolved PL measurement; Thin films | 公開日期: | 2020 | 卷: | 124 | 期: | 47 | 起(迄)頁: | 25729-25737 | 來源出版物: | Journal of Physical Chemistry C | 摘要: | In this study, exciton dynamics and singlet fission (SF) in amorphous rubrene thin films with various thicknesses from 5 to 100 nm were investigated. No clear X-ray diffraction peaks could be observed from these thin films, and their absorption and photoluminescence (PL) spectra were similar, although the PL slightly red-shifted with increasing rubrene thickness. However, temperature-dependent and time-resolved PL measurements showed dramatic differences between 5 and 100 nm thick films. There were two different relaxation channels in a 100 nm rubrene film, one of which is fission capable (channel a) and the other fission inactive (channel b). The SF process of species a was endothermic with activation energy 58 meV, as determined by time-resolved PL measurements carried out over a temperature range 300-77 K. On the other hand, for a 5 nm rubrene thin film, both this endothermic SF route and a weaker, exothermic SF channel below 160 K were observed with a SF rate of 0.22 ns-1. This was attributed to a new fission channel (channel c) that is probably due to molecular packing in the beginning of film growth. Channel c indicated a lower coupling molecular strength together with higher singlet energy that compensated the required thermal energy barrier for SF. A phase transition from amorphous to polycrystalline rubrene was observed when a thermal annealing treatment was applied to the 100 nm rubrene film. The PL spectral profile was dominated by microcrystals oriented with the crystal c-Axis parallel with the substrate, and these high density of SF "hotspots"increased the SF rate with only a weak temperature dependence from 120 to 300 K. ? 2020 ACS. All rights reserved. |
URI: | https://www.scopus.com/inward/record.uri?eid=2-s2.0-85096524667&doi=10.1021%2facs.jpcc.0c07887&partnerID=40&md5=f80f83f4c73a71f8a53b8e761a687ed2 https://scholars.lib.ntu.edu.tw/handle/123456789/581003 |
ISSN: | 19327447 | DOI: | 10.1021/acs.jpcc.0c07887 |
顯示於: | 電機工程學系 |
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