Rational Design of Low Band Gap Polymers for Efficient Solar Cells with High Open-Circuit Voltage: The Profound Effect of Me and Cl Substituents with a Similar van Der Waals Radius
Rational Design of Low Band Gap Polymers for Efficient Solar Cells with High Open-Circuit Voltage: The Profound Effect of Me and Cl Substituents with a Similar van Der Waals Radius
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用于高开路电压高效太阳能电池的低带隙聚合物的合理设计：具有相似范德华半径的 Me 和 Cl 取代基的深远影响
DOI：
10.1021/acsami.9b18278
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发表时间：
2019
影响因子：
9.5
通讯作者：
Renqiang Yang
中科院分区：
文献类型：
--
作者：
Xiao Kang;Di Zhou;Qian Wang;Dangqiang Zhu;Xichang Bao;Xiyue Yuan;Fushuai Liu;Yonghai Li;Shanlin Qiao;Renqiang Yang
通常，基于低带隙材料的光伏器件可以降低开路电压(VOC)，实现低带隙(例如1.6 eV)和高VOC(>；0.9V)之间的权衡是获得高效聚合物太阳能电池的关键，特别是对于高性能的半透明PSCs和串联太阳能电池。尽管已经做出了许多努力来解决这个问题，但大多数结果并不令人满意。本文针对聚合物的HOMO能级较深，以及弱的非共价氯···S相互作用导致主链平面性增强的特点，设计并合成了基于氯化方法和高效的噻唑诱导策略的聚合物PTBTz-Cl。此外，由于侧链具有相似的范德华半径(CH3：0.20 nm对Cl：0.18 nm)，因此构建了甲基取代聚合物PTBTz-Me作为参考。令人鼓舞的是，与PTBTz-2相比，新合成的聚合物在30 0~770 nm范围内表现出红移的吸收光谱，其∼为1.6 eV。然而，氯和Me取代基的作用是不同的。与聚合物PTBTz-Me相比，PTBTz-Cl具有HOMO值低、结晶性强、分子内相互作用更紧密的特点。因此，聚合物PtBTz-Cl表现出了优异的光伏性能，其VOC为0.94V，功率转换效率为10.35%，比基于PtBTz-Me的9.12%的效率提高了∼11%，也是聚合物/富勒烯太阳能电池中最高的值之一。此外，获得了0.64 eV的较小的光能损失，这在目前的高性能聚合物系统中是罕见的。
Generally, low band gap material-based photovoltaic devices have reduced open circuit voltage (VOC), and realizing the trade-off between the low band gap (Eg< 1.6 eV) and highVOC(>0.9 V) could be critical to give efficient polymer solar cells, especially for high-performance semitransparent PSCs and tandem solar cells. Although lots of efforts have been made to address the issue, most results have not been gratifying. In this work, the polymer PTBTz-Cl based on the chlorination method and efficient thiazole-induced strategy was designed and synthesized, aiming at the deep HOMO energy level, and the enhanced backbone planarity caused by the weak noncovalent Cl···S interaction. In addition, the methyl-substituted polymer PTBTz-Me was constructed as the reference due to the similar van der Waals radius of the side chain (CH3: 0.20 nm vs Cl: 0.18 nm). Encouragingly, in comparison with that of PTBTz-2, the newly synthesized polymers exhibit the red-shifted absorption spectra ranging from 300 to 770 nm, with an obviously reducedEgof ∼1.6 eV. However, the function of Cl and Me substituents is different. Compared to the polymer PTBTz-Me, PTBTz-Cl exhibits a lower HOMO value, stronger crystallinity, and more compact intramolecular interactions. Consequently, the polymer PTBTz-Cl exhibits excellent photovoltaic performance with a notableVOCof 0.94 V and a power conversion efficiency of 10.35%, which is ∼11% higher than the 9.12% efficiency based on PTBTz-Me, and is also one of the highest values among polymer/fullerene solar cells. Moreover, a smaller photo energy loss (Eloss) of 0.64 eV is achieved, which is rare among the current high-performance polymer systems.