Marked Consequences of Systematic Oligothiophene Catenation in Thieno[3,4-c]pyrrole-4,6-dione and Bithiopheneimide Photovoltaic Copolymers

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• 作者：Nanjia Zhou ; Xugang Guo ; Rocio Ponce Ortiz ; Tobias Harschneck ; Eric F. Manley ; Sylvia J. Lou ; Patrick E. Hartnett ; Xinge Yu ; Noah E. Horwitz ; Paula Mayorga Burrezo ; Thomas J. Aldrich ; Juan T. L贸pez Navarrete ; Michael R. Wasielewski ; Lin X. Chen ; Robert. P. H. Chang ; Antonio Facchetti ; Tobin J. Marks
• 刊名：Journal of the American Chemical Society
• 出版年：2015
• 出版时间：October 7, 2015
• 年：2015
• 卷：137
• 期：39
• 页码：12565-12579
• 全文大小：1073K
• ISSN：1520-5126

文摘

As effective building blocks for high-mobility transistor polymers, oligothiophenes are receiving attention for polymer solar cells (PSCs) because the resulting polymers can effectively suppress charge recombination. Here we investigate two series of in-chain donor鈥揳cceptor copolymers, PTPDnT and PBTInT, based on thieno[3,4-c]pyrrole-4,6-dione (TPD) or bithiopheneimide (BTI) as electron acceptor units, respectively, and oligothiophenes (nTs) as donor counits, for high-performance PSCs. Intramolecular S路路路O interaction leads to more planar TPD polymer backbones, however backbone torsion yields greater open-circuit voltages for BTI polymers. Thiophene addition progressively raises polymer HOMOs but marginally affects their band gaps. FT-Raman spectra indicate that PTPDnT and PBTInT conjugation lengths scale with nT catenation up to n = 3 and then saturate for longer oligomer. Furthermore, the effects of oligothiophene alkylation position are explored, revealing that the alkylation pattern greatly affects film morphology and PSC performance. The 3T with 鈥渙utward鈥?alkylation in PTPD3T and PBTI3T affords optimal 蟺-conjugation, close stacking, long-range order, and high hole mobilities (0.1 cm²/(V s)). These characteristics contribute to the exceptional 鈭?0% fill factors for PTPD3T-based PSCs with PCE = 7.7%. The results demonstrate that 3T is the optimal donor unit among nTs (n = 1鈥?) for photovoltaic polymers. Grazing incidence wide-angle X-ray scattering, transmission electron microscopy, and time-resolved microwave conductivity measurements reveal that the terthiophene-based PTPD3T blend maintains high crystallinity with appreciable local mobility and long charge carrier lifetime. These results provide fundamental materials structure-device performance correlations and suggest guidelines for designing oligothiophene-based polymers with optimal thiophene catenation and appropriate alkylation pattern to maximize PSC performance.