Measurement of Exciton Diffusion in a Well-Defined Donor/Acceptor Heterojunction based on a Conjugated Polymer and Cross-Linked Fullerene Derivative

详细信息    查看全文

• 作者：Yanbin Wang ; Hiroaki Benten ; Shunji Ohara ; Daichi Kawamura ; Hideo Ohkita ; Shinzaburo Ito
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2014
• 出版时间：August 27, 2014
• 年：2014
• 卷：6
• 期：16
• 页码：14108-14115
• 全文大小：452K
• ISSN：1944-8252

文摘

We designed a well-defined donor/acceptor heterojunction for measuring exciton diffusion lengths in conjugated polymers. To obtain an insoluble electron acceptor layer, a new cross-linkable fullerene derivative (bis-PCBVB) was synthesized by functionalizing [6,6]-diphenyl-C₆₂-bis(butyric acid methyl ester) (bis-PCBM) with two styryl groups. The spin-coated bis-PCBVB film was cross-linked in situ by heating at 170 掳C for 60 min. Surface characterizations by UV鈥搗isible absorption, atomic force microscopy, and photoelectron yield spectroscopy revealed that a smooth and solvent-resistant film (p-PCBVB) was obtained. In bilayer films with a donor conjugated polymer, poly[2,7-(9,9-didodecylfluorene)-alt-5,5-(4鈥?7鈥?bis(2-thienyl)-2鈥?1鈥?3鈥?benzothiadiazole)] (PF12TBT), spin-coated on top of the p-PCBVB acceptor layer, the photoluminescence (PL) of the PF12TBT was effectively quenched. This is because the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the p-PCBVB film are nearly the same as those of the parent bis-PCBM spin-coated film. On the basis of the PL quenching results, the exciton diffusion length and exciton diffusion coefficient in the PF12TBT were evaluated to be 11 nm and 9.8 脳 10^鈥? cm² s^鈥?, respectively.

Keywords:

exciton diffusion length; exciton diffusion coefficient; cross-linking; fullerene; conjugated polymer; fluorene-based copolymer; fluorescence quenching; planar heterojunction