Spin-Coated Thin Films of Polycyclic Aromatic Hydrocarbons Exhibiting High SCLC Hole Mobilities

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• 作者：Yong Li ; Robert G. Clevenger ; Lu Jin ; Kathleen V. Kilway ; Zhonghua Peng
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：January 21, 2016
• 年：2016
• 卷：120
• 期：2
• 页码：841-852
• 全文大小：744K
• ISSN：1932-7455

文摘

High charge carrier mobilities have been greatly sought after in the development of cutting-edge organic electronic and optoelectronic devices. Although high field-effect transistor hole mobilities have been reported for solution-processed organic semiconductor thin films, their space-charge-limited current (SCLC) mobilities are still substantially lower. Herein, we report the synthesis and thin film SCLC hole mobilities of four polycyclic aromatic hydrocarbons, specifically, 2,5,8,17-tetra-tert-butyldiacenaphtho[1,2-j:1′,2′-l]fluoranthene (1), 2,5,8,11,14,17-hexa-tert-butyldiacenaphtho[1,2-j:1′,2′-l]fluoranthene (2), 2,9,12,15-tetra-tert-butylacenaphtho[1,2-j]benzo[l]fluoranthene (3), and 2,9,12,15-tetra-tert-butyl-4,5,6,7-tetraphenylacenaphtho[1,2-j]benzo[l]fluoranthene (4). Spin-coated pristine thin films of compounds 1–4 exhibit SCLC hole mobilities of 1.18 ± 0.18 × 10^–3, 3.8 ± 0.9 × 10^–5, 2.00 ± 0.87 × 10^–3, and 2.27 ± 0.67 × 10^–4 cm² V^–1 s^–1, respectively. Upon thermal annealing at 120 °C for 10 min, compounds 1, 2, and 4 show limited changes in their optical properties and hole mobilities. In contrast, thermal annealing of thin films of 3 leads to broadened and red-shifted absorptions and emissions as well as drastically improved SCLC hole mobilities as high as 3.4 ± 0.1 × 10^–1 cm² V^–1 s^–1, one of the highest ever recorded SCLC hole mobilities on solution-processed organic semiconductor thin films. This improvement of the hole mobilities for the thin films of 3 is attributed to its radically enhanced crystallinity and intermolecular π–π overlap. Expansion of compound 3’s acene core with the hopes of further strengthening the π–π stacking interaction and thus further improving the SCLC mobility was unfortunately unsuccessful as the resulting molecule exhibits poor film formation properties.