Control of Mesoscale Morphology and Photovoltaic Performance in Diketopyrrolopyrrole-Based Small Band Gap Terpolymers

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• 作者：Long Ye ; Xuechen Jiao ; Shaoqing Zhang ; Huifeng Yao ; Yunpeng Qin ; Harald Ade and Jianhui Hou
• 刊名：Advanced Energy Materials
• 出版年：2017
• 出版时间：February 8, 2017
• 年：2017
• 卷：7
• 期：3
• 全文大小：2742K
• ISSN：1614-6840

文摘

Morphology control is one of the key strategies in optimizing the performance of organic photovoltaic materials, particularly for diketopyrrolopyrrole (DPP)-based donor polymers. The design of DPP-based polymers that provide high power conversion efficiency (PCE) presents a significant challenge that requires optimization of both energetics and morphology. Herein, a series of high performance, small band gap DPP-based terpolymers are designed via two-step side chain engineering, namely introducing alternating short and long alkyls for reducing the domain spacing and inserting alkylthio for modulating the energy levels. The new DPP-based terpolymers are compared to delineate how the side chain impacts the mesoscale morphology. By employing the alkylthio-substituted terpolymer PBDPP-TS, the new polymer solar cell (PSC) device realizes a good balance of a high V_oc of 0.77 V and a high J_sc over 15 mA cm⁻², and thus realizes desirable PCE in excess of 8% and 9.5% in single junction and tandem PSC devices, respectively. The study indicates better control of domain purity will greatly improve performance of single junction DPP-based PSCs toward 10% efficiency. More significantly, the utility of this stepwise side chain engineering can be readily expanded to other classes of well-defined copolymers and triggers efficiency breakthroughs in novel terpolymers for photovoltaic and related electronic applications.