摘要
分别以绕丹宁和噻唑烷-2,4-二酮单元为端基、IDT为中心核设计合成了一个新型不对称结构的有机小分子受体IDT-2,并通过与两端均以绕丹宁或噻唑烷-2,4-二酮受体单元的对称小分子受体IDT-1和IDT-3进行对比,探讨了分子结构与性能之间的关系。研究发现,从IDT-1到IDT-3,随着两端的绕丹宁基团被噻唑烷-2,4-二酮基团逐步取代,这类小分子受体的吸收光谱显著蓝移,光学带隙E_g^(opt)逐步增大,LUMO和HOMO能级也逐渐抬升。随后我们分别以这三个小分子为受体、P3HT为给体共混构建活性层而制备了有机太阳能电池,结果表明,以两端均为绕丹宁单元的对称结构小分子受体IDT-1构建的电池器件具有最高的光电转换效率(PCE),相应的J_(sc)和FF值也最大,而V_(oc)则最低;而以两端均为噻唑烷-2,4-二酮基团的对称结构小分子受体IDT-3的电池器件,其V_(oc)最高,但其J_(sc)和FF则最低,PCE值也最小。对于IDT-2而言,由于分子只有一个绕丹宁单元被噻唑烷-2,4-二酮所取代,其V_(oc),J_(sc)和PCE均介于IDT-1与IDT-3之间。由此说明,尽管噻唑烷-2,4-二酮基团的引入能有效提升器件V_(oc),但却不利于改善其J_(sc)和FF,因此受体的分子设计中如何平衡电池器件的几种光伏性能参数而获得高的光电转换效率仍是十分重要的研究课题之一。
As reported previously, rhodanine and thiazolidine-2,4-dione units have been widely used as the terminal group to construct the efficient non-fullerene small molecular acceptors with the structure of A1-A2-D-A2-A1. Compared with the acceptor using thiazolidine-2,4-dione unit as the terminal group, the acceptor with rhodanine unit as the terminal electron-withdrawing group usually showed the improved short circuit current density (Jsc) and fill factor (FF) as well as the higher power conversion efficiency (PCE), regardless of the lower open circuit voltage (Voc). However, the causes of difference are still not very clear. Therefore, in this work, an unsymmetrical organic acceptor (IDT-2) has been designed and synthesized with rhodanine and thiazolidine- 2,4-dione units as the electron-withdrawing terminal groups to connect an indacenodithiophene (IDT) central core, respectively. By comparing with the two analogues of the symmetrical organic acceptors based on rhodamine unit (IDT-1) or thiazolidine-2,4-dione unit (IDT-3) as the terminal group, the structure-property relationship has been investigated for this series of acceptors. It is found that as two rhodamine terminal groups are replaced step by step with the thiazolidine-2,4-dione unit from IDT-1 to IDT-3, the ICT absorption of these small molecular acceptors is significantly blue-shifted from 633 (soln)/656 (film), 618/645 to 603/625 nm, and the corresponding optical band gap (Eg opt) is also gradually widened from 1.68, 1.71 to 1.77 eV for IDT-1, IDT-2 and IDT-3, respectively, which can be attributed to the introduction of thiazolidine-2,4-dione unit to reduce the stability of quinoid structure of the conjugation backbone. At the same time, the LUMO/HOMO (the lowest unoccupied molecular orbital/the highest occupied molecular orbital) energy levels of the molecules are gradually uplifted to be ?3.62/?5.58,?3.60/?5.56, and ?3.57/?5.53 eV, respectively, which is generally beneficial for the improvement of the Voc due to the upshifted LUMO energy levels of the a
作者
杨阳
蒋秀
占肖卫
陈兴国
YANG Yang;JIANG Xiu;ZHAN Xiaowei;CHEN Xingguo(Hubei Key Laboratory on Organic and Polymeric Opto-electronic Materials, College of Chemistry and Molecular Sciences, WuhanUniversity, Wuhan 430072, P. R. China;Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, P. R. China.)
出处
《物理化学学报》
SCIE
CAS
CSCD
北大核心
2019年第3期257-267,共11页
Acta Physico-Chimica Sinica
基金
国家自然科学基金(51173138)资助项目~~
