Conjugation Pathway of Benzobisoxazoles in Polymer Donors Mediates the Charge Management and Enables Organic Solar Cells with Record Certified Efficiency
Miao Liu, Lunbi Wu, Yulong Hai, Yongmin Luo, Yao Li, Rouren Chen, Yue Ma, Tao Jia, Qingduan Li, Sha Liu, Sha Liu, Ruijie Ma, Yue‐Peng Cai, Jiaying Wu, Gang Li, Shengjian Liu, Shengjian Liu
Abstract
Abstract Charge management plays a pivotal role in achieving high‐performance bulk heterojunction (BHJ) organic solar cells (OSCs). In this study, two efficient polymer donors are designed, P[4,8]BBO and P[2,6]BBO, by regulating the conjugation pathways of benzobisoxazoles (BBO) through 4,8‐ and 2,6‐linkages, respectively. Comparing to P[2,6]BBO, the isomer of conjugation pathway has been proved to enable P[4,8]BBO a shallower highest occupied molecular orbital (HOMO) energy level of −5.20 eV, significantly enhanced luminescence efficiency, and reduced aggregation property. These improvements lead to a dramatic increase in device efficiencies from 2.6% for P[2,6]BBO:eC9‐2Cl to 19.0% for P[4,8]BBO:eC9‐2Cl. The combined characterizations show that a better comprehensive charge management can be reached in P[4,8]BBO:eC9‐2Cl‐based OSCs, yielding a significantly higher short‐circuit current density ( J SC ) and fill factor (FF) parameters compared to P[2,6]BBO:eC9‐2Cl‐based ones. Furthermore, P[4,8]BBO demonstrates good applicability and can achieve an impressive efficiency of 19.4% in all‐polymer solar cells with a third‐party certified efficiency of 19.1%. This work highlights the critical role of conjugation pathway isomerism in mediating polymeric properties and advancing the development of high‐performance multifunctional photovoltaic materials.