New Semiconductors Based on 2,2鈥?Ethyne-1,2-diylbis[3-(alk-1-yn-1-yl)thiophene] for Organic Opto-Electronics

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• 作者：Pierre-Luc T. Boudreault ; Jonathan W. Hennek ; Stephen Loser ; Rocio Ponce Ortiz ; Brian J. Eckstein ; Antonio Facchetti ; Tobin J. Marks
• 刊名：Chemistry of Materials
• 出版年：2012
• 出版时间：August 14, 2012
• 年：2012
• 卷：24
• 期：15
• 页码：2929-2942
• 全文大小：709K
• 年卷期：v.24,no.15(August 14, 2012)
• ISSN：1520-5002

文摘

We report the synthesis and properties of three novel acetylenic materials based on the new electron-rich building block, 2,2鈥?ethyne-1,2-diylbis[3-(alk-1-yn-1-yl)thiophene] (EBT). The synthesis of this new nonacene core is efficient and straightforward, and variation among n-hexyl, n-tetradecyl, and 2-ethylhexyl substituents substantially impacts the materials properties. Appending 2-ethylhexyl substituted diketopyrrolopyrrole (DPP) units to either terminus of the EBT core yields a series of low band gap molecules that are characterized in detail by a range of experimental microstructure and electronic structure probes and by density functional theory (DFT) computation. Detailed morphology/microstructure characterization of spin-cast films by X-ray diffraction and AFM reveals instructive microstructure and electronic/photovoltaic response relationships in both organic field-effect transistors and bulk-heterojunction organic photovoltaic cells. Thus, the former devices exhibit hole mobilities (渭_h) as large as 0.2 cm²/(V s) which fall as thermal annealing increases long-range order. The latter devices using PC₆₁BM as the electron acceptor exhibit power conversion efficiencies as high as 2%, which appear to fall as the materials become less ordered. These results are in accord with a model where evolving grain boundaries and crystallinity impedes hole transport and excitonic charge generation.

Keywords:

OTFTs; OPVs; arylacetylene; EBT; small molecules