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Significantly Enhanced Molecular Stacking in Ternary Bulk Heterojunctions Enabled by an Appropriate Side Group on Donor Polymer
摘要： Ternary strategy is a promising approach to broaden the photoresponse of polymer solar cells (PSCs) by adopting combinatory photoactive blends. However, it could lead to a more complicated situation in manipulating the bulk morphology. Achieving an ideal morphology that enhances the charge transport and light absorption simultaneously is an essential avenue to promote the device performance. Herein, two polymers with different lengths of side groups (P1 is based on phenyl side group and P2 is based on biphenyl side group) are adopted in the dual-acceptor ternary systems to evaluate the relationship between conjugated side group and crystalline behavior in the ternary system. The P1 ternary system delivers a greatly improved power conversion efficiency (PCE) of 13.06%, which could be attributed to the intense and broad photoresponse and improved charge transport originating from the improved crystallinity. Inversely, the P2 ternary device only exhibits a poor PCE of 8.97%, where the decreased device performance could mainly be ascribed to the disturbed molecular stacking of the components originating from the overlong conjugated side group. The results demonstrate a conjugated side group could greatly determine the device performance by tuning the crystallinity of components in ternary systems.
关键词： ternary systems,ternary bulk heterojunctions,complementary absorption,polymer solar cells,molecular stacking,side chain effect
更新于2025-09-23 15:19:57
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Cyclopentadithiophene cored A-π-D-π-A non-fullerene electron acceptor in ternary polymer solar cells to extend the light absorption up to 900?nm
摘要： Conjugated small molecular non-fullerene electron acceptors (NFA) are considered as one of the critical materials for achieving high performance and low cost of polymer solar cells, and received much attention in the last few years. However, most of the NFAs are based on large fused π-aromatic core, which requires complicate synthesis efforts. In addition, the relatively weak light absorption limited to 800 nm of most the NAFs limits the energy harvesting capability of the solar cells. In this paper, we report an A-π-D-π-A type molecule cored with a cyclopentadithiophene unit, which can be easily synthesized in two steps from commercially available starting materials. This compound shows a broad absorption up to 900 nm in thin solid film, which is ascribed to the relatively high highest occupied molecular orbital (HOMO) energy level as confirmed by cyclic voltammery and theoratical calculation. Application of the compound in polymer solar cells was also investigated both in binary and in ternary systems. The optimized power conversion efficiency (PCE) in binary solar cell with PTB7-Th as donor is 5.76% with an open circuit voltage (VOC) of 0.838 V, a short circuit current (JSC) of 14.81 mA/cm2 and a fill factor (FF) of 46.4%. In the ternary solar cells which includes a second acceptor, PC71BM, the highest PCE achieved is 9.39% with a VOC of 0.803 V, a JSC of 19.01 mA/cm2, a FF of 61.6%, which is over 20% enhancement compared to the PTB7-Th:PC71BM system (PCE of 7.58%). This work develops a simple small molecule non-fullerene acceptor which can largely enhance the photo response in near infrared region to improve the performance of fullerene based organic solar cell.
关键词： Light absorption,Non-fullerene electron acceptor,Cyclopentadithiophene,Ternary systems,Polymer solar cells
更新于2025-09-12 10:27:22