Profound Influences of Two-Dimensional Side Chains Regional Transfer on Crystallinity and Photovoltaic Performance of Donor Polymers

The emergence of donor polymers with two-dimensional configurations has greatly facilitated the development of organic solar cells. Herein, benzo[1,2-b:4,5-b’]dithiophene- dithieno[3,2-f:2′,3′-h]quinoxaline (BDT-DTQ) backbone was used as a control unit, while polymers PQR16-BTF and PQTF-BO with 2d configuration on donor or acceptor unit were synthesized to study the impact of 2d side chain migration on polymer performance. PQR16-BTF exhibits a more uniform electron distribution and stronger intermolecular interactions, making it easier to achieve long-range ordered molecular crystallization. Especially in the blend film, molecular crystallization can be further enhanced, and the PQR16-BTF:PY-IT device achieved an efficiency of 13.61% and a fill factor of 69%, which means that the polymers with a 2d configuration donor unit are more likely to achieve good device performance. PQTF-BO exhibited an increased acceptor unit area and single-component crystallization, but its localized electron distribution and weaker intermolecular interactions severely affected the miscibility and crystallinity of the blend film. The PQTF-BO:PY-IT device achieved an efficiency of 11.7% and a fill factor of 58%. Interestingly, the wide absorption and low nonradiative loss of the polymers with 2d configuration acceptor unit are beneficial to enhance the short-circuit current density and open-circuit voltage of the devices. This work provides ideas for the design of two-dimensional configuration polymers.

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