基于无规三元共聚物的非卤溶液加工型高效聚合物太阳能电池

在本工作中，我们以烷硫基噻吩基取代的苯并二噻吩(BDTT-S)为给体单元、5, 6-二氟取代苯并三唑(FBTz)和噻唑并噻唑(TTz)为弱吸收电子受体单元，设计合成了一系列宽带隙的无规三元共聚物给体材料。通过改变两个受体单元FBTz和TTz在聚合物中的摩尔比，有效调节了聚合物的光学、电化学、分子排列以及电荷传输性能。最终，使用非卤溶剂为加工溶剂，以三元共聚物PSBTZ-60为给体、ITIC为非富勒烯受体的聚合物太阳能电池(PSCs)获得了10.3%的能量转换效率(PCE)，其中开路电压为0.91 V，短路电流为18.0 mA·cm^?2，填充因子为62.7%；与之相比，在相同的器件制备条件下，基于PSTZ:ITIC的PSCs仅获得8.5%的PCE，基于PSBZ:ITIC的PSCs也仅获得8.1%的PCE。这些结果表明：三元无规共聚能够作为一种简单且实用的策略去设计、合成高性能聚合物光伏材料。

Wide Bandgap Random Terpolymers for High Efficiency Halogen-Free Solvent Processed Polymer Solar Cells

Over the past two decades, bulk heterojunction polymer solar cells (PSCs) have attracted significant attention owing to their potential applications in the mass fabrication of flexible device panels by roll-to-roll printing. To improve the photovoltaic performance of PSCs, much effort has been devoted to the optimization of properties of donor-acceptor (D-A) type polymer donor materials. Until now, the development of high-performance donor polymers is mainly dependent on the design and synthesis of binary polymers with a regular D/A alternating skeleton. Compared to binary polymers, random terpolymers with three different donor or acceptor monomer units possess synergetic effects of their inherent properties, such as optical absorption ability, energy levels, crystallinity, charge mobility, and morphological compatibility with the n-OS acceptors with suitable adjustment of the molar ratio of the three monomers. However, the irregularity in the polymer backbone of the random terpolymers may have an adverse effect on molecular packing, crystallinity, and charge mobility. Therefore, design and synthesis of high-performance terpolymers for PSCs is a challenging task. In this study, a series of wide bandgap random terpolymers PSBTZ-80, PSBTZ-60, and PSBTZ-40 based on alkylthiothienyl substituted benzodithiophene as the donor unit and two weak electron-deficient acceptor units of 5, 6-difluorobenzotriazole (FBTz) and thiazolothiazole (TTz) were designed and synthesized for PSC applications. The optical, electrochemical, molecular packing, and photovoltaic properties of the polymers were effectively modulated by varying the FBTz:TTz molar ratio. Therefore, the PSC based on PSBTZ-60 as the donor material and narrow bandgap small molecule 3, 9-bis(2-methylene-(3-(1, 1-dicyanomethylene)-indanone))-5, 5, 11, 11-tetrakis(4-hexyl-phenyl)-dithieno2, 3-d:2', 3'-d']-s-indaceno1, 2-b:5, 6-b']di thiophene) (ITIC) as the acceptor, processed using halogen-free solvents, exhibited high power conversion efficiency (PCE) of 10.3% with high open-circuit voltage (V_oc) of 0.91 V, improved short-circuit current density (J_sc) of 18.0 mA?cm^?2, and fill factor (FF) of 62.7%, which are superior to those of PSCs based on binary polymers PSBZ (a PCE of 8.1%, V_oc of 0.89 V, J_sc of 14.7 mA?cm^?2, and FF of 61.5%) and PSTZ (a PCE of 8.5%, V_oc of 0.96 V, J_sc of 14.9 mA?cm^?2, and FF of 59.1%). These results indicate that random terpolymerization is a simple and practical strategy for the development of high-performance polymer photovoltaic materials.