Fluorinated Benzoselenadiazole-Based Low-Band-Gap Polymers for High Efficiency Inverted Single and Tandem Organic Photovoltaic Cells

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• 作者：Ji-Hoon Kim ; Seung Ah Shin ; Jong Baek Park ; Chang Eun Song ; Won Suk Shin ; Hoichang Yang ; Yongfang Li ; Do-Hoon Hwang
• 刊名：Macromolecules
• 出版年：2014
• 出版时间：March 11, 2014
• 年：2014
• 卷：47
• 期：5
• 页码：1613-1622
• 全文大小：701K
• 年卷期：v.47,no.5(March 11, 2014)
• ISSN：1520-5835

文摘

We designed and synthesized two low-band-gap conjugated copolymers with alternating difluorinated benzoselenadiazole (DFDTBSe) and ethylhexyloxy (EH)- or octyldodecyloxy (OD)-substituted benzo[1,2-b:4,5-b鈥瞉dithiophene (BDT) building blocks. PEHBDT-DFDTBSe and PODBDT-DFDTBSe have optical band gap energies of 1.66 and 1.69 eV, respectively, and HOMO energy levels of 鈭?.44 and 鈭?.43 eV, respectively. The different alkyloxy side chains in the polymers affect the molecular packing and ordering in active-layer films blended with [6,6]-phenyl-C₇₁ butyric acid methyl ester (PC₇₁BM). The PEHBDT-DFDTBSe:PC₇₁BM film comprises predominantly 鈥渇ace-on鈥?crystal structures with short 蟺鈥撓€ stacking distances (3.69 脜) while PODBDT-DFDTBSe:PC₇₁BM has mostly 鈥渆dge-on鈥?structures according to two-dimensional grazing-incidence X-ray diffraction analysis. Bulk heterojunction solar cells were fabricated with an inverted structure of ITO/ethoxylated polyethylenimine/polymer:PC₇₁BM/MoO₃/Ag. The device fabricated using the PEHBDT-DFDTBSe:PC₇₁BM active layer shows a maximum power conversion efficiency (PCE) of up to 5.74%, which is the highest value reported for OPVs containing benzoselenadiazole and BDT-derivative polymers. A tandem solar cell was also fabricated using PEHBDT-DFDTBSe:PC₇₁BM and poly(3-hexylthiophene):indene-C₆₀-bisadduct as the top and bottom cell components, respectively; its maximum PCE was 7.15%.