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A Nonfullerene Acceptor with Alkylthio‐ and Dimethoxy‐Thiophene‐Groups Yielding High‐Performance Ternary Organic Solar Cells
摘要： Herein, an A–D–A-type nonfullerene acceptor (named IDTS-4F) with an alkyl thiophenyl side chain and dimethoxy thiophene bridging unit is reported. The use of an alkyl thiophenyl group is important, as the insertion of sulfur atoms can slightly downshift the highest occupied molecular orbital (HOMO) level of the molecule and allows IDTS-4F to match with state-of-the-art donor polymer PM6 (or PM7). Compared with conventional nonfullerene acceptors, IT-4F, the IDTS-4F molecule, has a smaller optical bandgap and higher lowest unoccupied molecular orbital (LUMO) level, which are beneficial to increase the Voc and Jsc of the devices. Nonfullerene organic solar cell devices are fabricated using IDTS-4F. Although the binary device based on IDTS-4F exhibits a lower fill factor (FF, 70%), the ternary device by incorporating 0.2 of IDTS-4F and 0.8 of IT-4F (with PM6 as the donor polymer) can simultaneously achieve a higher Voc and Jsc, while maintaining the high FF (77%) of IT-4F based system. Morphology characterizations indicate the formation of homogeneous film morphology, the large increase in phase purity and crystallinity, and the reduction in domain size upon addition of crystalline IDTS-4F, while the electron/hole mobilities and recombination losses of the IT-4F system are both maintained.
关键词： polymer solar cells,nonfullerene acceptors,fullerene-free,organic solar cells,ternary solar cells
更新于2025-09-19 17:13:59
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Fusion or non-fusion of quasi-two-dimensional fused perylene diimide acceptors: the importance of molecular geometry for fullerene-free organic solar cells
摘要： In this work, two small molecular electron acceptor (BT-FPDI and fBT-FPDI) comprising a central bithiophene (BT) bridge and two fused perylene diimide (FPDI) units were designed and synthesized for fullerene-free organic solar cells (OSCs). The molecular geometry of these electron acceptors can be adjusted through a locked conformation via photocyclization reaction. As expected, BT-FPDI has a highly twisted geometry with the assistance of the quasi-two-dimensional (quasi-2D) configuration of FPDI unit and modest dihedral angles between FPDI and BT units, while fBT-FPDI shows a relatively planar geometry with symmetrically aligned the FPDI wings. When pairing with polymer donor PTB7-Th, the intrinsic configuration characteristic of BT-FPDI guaranteed an impressive power conversion efficiency (PCE) of 8.07% with an open circuit voltage (Voc) of 0.81 V, and a recorded high short-circuit current density (Jsc) of 17.35 mA/cm2, which is almost the highest Jsc value reported in PDI-based fullerene-free OSCs. However, the optimal device employing fBT-FPDI as electron acceptor only delivered a PCE of 5.89% with a significantly reduced Jsc of 12.30 mA/cm2. The interesting result show that, unlike traditional PDI molecules, the ring-fusion molecular design has not produce the desired positive effect in FPDI derivatives, and also provide a new insight into the regulation of the molecular geometry based on FPDI acceptors with intrinsic quasi-2D structure.
关键词： perylene diimide,molecular geometry,fullerene-free organic solar cells,ring-fusion,power conversion efficiency
更新于2025-09-11 14:15:04