Crystallization and Optical Compensation by Fluorinated Rod Liquid Crystals for Ternary Organic Solar Cells
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- 作者：Xunfan Liao ; Feiyan Wu ; Lie Chen ; Yiwang Chen
- 刊名：Journal of Physical Chemistry C
- 出版年：2016
- 出版时间：August 25, 2016
- 年：2016
- 卷：120
- 期：33
- 页码：18462-18472
- 全文大小：890K
- 年卷期：0
- ISSN：1932-7455
文摘
Cyanobiphenyl type liquid crystal molecules used as additives for polymer solar cells (PSCs) have been proved as a promising strategy to increase donor crystallinity, short circuit current density (Jsc) and result in a higher power conversion efficiency (PCE) of PSCs. However, they would sacrifice light absorption in long wavelength region due to their large bandgap and weak absorbance. To overcome this shortage, a fluorinate donor–acceptor–donor rodlike liquid crystal (RLC), 5,6-difluoro-4,7-bis(5′-hexyl-[2,2′-bithiophen]-5-yl)benzo[c][1,2,5]thiadiazole (DFBT-TT6), is designed and synthesized as additive for bulk-heterojunction organic solar cells. DFBT-TT6 shows a broad absorption from 300 to 650 nm. Quite different from the commonly used liquid crystal additives, DFBT-TT6 can effectively compensate the energy loss of P3HT in the short wavelength without sacrificing the absorbance in long wavelength region. Remarkably, grazing incident X-ray diffraction (GIXRD), electron microscopy, and X-ray photoelectron spectroscopy (XPS) prove that, driven by the cooperative effect of the RLC orientation and its surface segregation, a favorable morphology with improved crystallinity of poly(3-hexyl)thiophene (P3HT) in the active layer has been developed. Therefore, incorporation of DFBT-TT6 into P3HT: [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend achieved an improved PCE from 2.34% to 3.91% with an increased Jsc, fill factor (FF), and charge mobility.