B-N-bond-embedded triplet terpolymers with small singlet-triplet energy gaps for suppressing non-radiative recombination and improving blend morphology in organic solar cells

• Main Authors: Pang, Bo, Liao, Chentong, Xu, Xiaopeng, Peng, Shaoqian, Xia, Jianlong, Guo, Yuanyuan, Xie, Yuan, Chen, Yuting, Duan, Chunhui, Wu, Hongbin, Li, Ruipeng, Peng, Qiang
• Other Authors: School of Physical and Mathematical Sciences
• Format: Article
• Language: English
• Published: 2024
• Subjects: Science::Physics; Non-Radiative Recombination; Organic Solar Cells
• Online Access: https://hdl.handle.net/10356/172937
• Institution: Nanyang Technological University

Suppressing the photon energy loss (Eloss ), especially the non-radiative loss, is of importance to further improve the device performance of organic solar cells (OSCs). However, typical π-conjugated semiconductors possess a large singlet-triplet energy gap (ΔEST ), leading to a lower triplet state than charge transfer state and contributing to a non-radiative loss channel of the photocurrent by the triplet state. Herein, a series of triplet polymer donors are developed by introducing a BNIDT block into the PM6 polymer backbone. The high electron affinity of BNIDT and the opposite resonance effect of the B-N bond in BNIDT results in a lowered highest occupied molecular orbital (HOMO) and a largely reduced ΔEST . Moreover, the morphology of the active blends is also optimized by fine-tuning the BNIDT content. Therefore, non-radiative recombination via the terminal triplet loss channels and morphology traps is effectively suppressed. The PNB-3 (with 3% BNIDT):L8-BO device exhibits both small ΔEST and optimized morphology, favoring more efficient charge transfer and transport. Finally, the simultaneously enhanced Voc of 0.907 V, Jsc of 26.59 mA cm-2 , and FF of 78.86% contribute to a champion PCE of 19.02%. Therefore, introducing B-N bonds into benchmark polymers is a possible avenue toward higher-performance of OSCs.