Abstract
Two new wide-bandgap polythiophenes, i.e., poly[5,5′-bis(2-hexyldecyl)-(2,2′-bithiophene)-4,4′-dicarboxylate-alt-5,5′-3-chloro-2,2′-bithiophene] (PDCBT-Cl) and poly[5,5′-bis(2-hexyldecyl)-(2,2′-bithiophene)-4,4′-dicarboxylate-alt-5,5′-3,3′-dichloro-2,2′-bithiophene] (PDCBT-2Cl) comprising 3-chloro-2,2′-bithiophene and 3,3′-dichloro-2,2′-bithiophene moieties, respectively, were synthesized for fullerene-free polymer solar cells (PSCs). For comparison, three other polymers based on [2,2′-bithiophene]-4,4′-dicarboxylate (DCBT), i.e., PDCBT, PDCBT-F, and PDCBT-2F with 2,2′-bithiophene, 3-fluoro-2,2′-bithiophene, and 3,3′-difluoro-2,2′-bithiophene as comonomers, respectively, were also prepared. PSC devices were fabricated with these polymers as donor materials and ITIC-Th1 as acceptor. The incorporation of chlorine (Cl) or fluorine (F) atoms into polymers both efficiently downshifted the highest occupied molecular orbital (HOMO) energy levels, leading to higher open-circuit voltage (Voc) in the PSCs. Owing to the proper phase-separated morphology with favorable molecular packing and miscibility, the device based on PDCBT-Cl:ITIC-Th1 exhibited efficient exciton dissociation and charge collection as well as weak charge recombination and thereby displayed the best power conversion efficiency (PCE) up to 12.38%. The devices based on other polymers showed inferior PCEs (8.14% for PDCBT, 10.85% for PDCBT-F, 8.48% for PDCBT-2F, and 6.94% for PDCBT-2Cl). The monomers that are used to make PDCBT-Cl can be synthesized in relatively large scale from commercial available chemicals. All these indicate that PDCBT-Cl is a promising donor material for the large area fabrication of high-performance fullerene-free PSCs.
| Original language | English |
|---|---|
| Pages (from-to) | 4464-4474 |
| Number of pages | 11 |
| Journal | Macromolecules |
| Volume | 52 |
| Issue number | 12 |
| DOIs | |
| Publication status | Published - 25 Jun 2019 |
Funding
†School of Materials Science and Engineering, Tianjin University, Tianjin 300072, P. R. China ‡Tianjin Key Laboratory of Molecular Optoelectronic Science, Tianjin University, and Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, P. R. China §Molecular Materials and Nanosystems and Institute for Complex Molecular Systems, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands ∥Beijing National Laboratory for Molecular Science and State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China ⊥State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China This work is supported by the National Natural Science Foundation of China (No. 21574128 and 51703158). The research also received funding from the European Research Council (ERC Grant Agreement No. 33903). The authors thank the Beijing Synchrotron Radiation Facility (BSRF) for the help with 2D GIWAXS measurements.