Bandgap and molecular energy level control. of conjugated polymer photovoltaic materials based on benzo[1,2-b: 4,5-b']dithiophene
Bandgap and molecular energy level control. of conjugated polymer photovoltaic materials based on benzo[1,2-b: 4,5-b']dithiophene
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DOI：
10.1021/ma800820r
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发表时间：
2008-08-26
期刊：
影响因子：
5.5
通讯作者：
Yang, Yang
中科院分区：
文献类型：
--
作者：
Hou, Jianhui;Park, Mi-Hyae;Yang, Yang
带隙和分子能级控制对于提高共轭聚合物的光伏性能非常重要。调节这些参数的常见方法是通过与不同单元共聚来改变共轭聚合物的结构。本文的研究工作重点是不同共轭单元的苯[1,2-b:4,5-b']二噻吩（BDT）的合成及其光伏性能。合成了八种具有常用共轭单元的新型BDT聚合物，包括噻吩、苯并[c][1,2,5]噻二唑(BT)、噻吩并[3,4-b]吡嗪(TPZ)等。聚合物的带隙可在1.0-2.0 eV范围内调节，并且其HOMO和LUMO能级也可以有效调节。系统地研究了这些聚合物的吸收光谱以及电化学和光伏性能。一些表现出相同的带拉链降低效果的单元对聚合物的分子能级表现出不同的效果。例如，TPZ单元可以通过降低LUMO能级和提高聚合物的HOMO能级来减小带隙，但BT单元只能通过降低LUMO能级来降低带隙。由于异质结聚合物太阳能电池的开路电压（V-oc）被认为与电子给体材料的HOMO能级成反比，因此基于H9（BDT和TPZ的共聚物）的器件的V i 约为。比基于 BDT 和 BT 的共聚物 H7 的器件低 0.5 V。本文研究和讨论了七种常用单元对BDT基聚合物带隙、分子能级和光伏性能的影响，不仅可以为光伏材料的设计提供指导，而且可以为各种其他电子器件的材料提供指导。此外，基于PCBM和BDT基聚合物之一H6的器件PCE达到1.6%，器件的V-oc、I-sc和FF分别为0.75 V、3.8 mA/cm(2)和56%，这表明BDT是一种有前途的光伏共轭聚合物通用单元。由于我们开发了4,8-双烷氧基-BDT单体的合成方法，BDT单元将在未来的共轭聚合物设计研究中发挥重要作用。
Bandgap and molecular energy level control are of great importance in improving photovoltaic properties of conjugated polymers. A common approach to tuning these parameters is to modify the structure of conjugated polymers by copolymerizing with different units. In this paper, research work focuses on the synthesis of benzol [1,2-b:4,5-b']dithiophene (BDT) with different conjugated units and their photovoltaic performance. Eight new BDT-based polymers with commonly used conjugated units, including thiophene, benzo[c][1,2,5]thiadiazole (BT), thieno[3,4-b]pyrazine (TPZ), etc., were synthesized. The bandgaps of the polymers were tuned in the range of 1.0-2.0 eV, and their HOMO and LUMO energy levels could also be tuned effectively. The absorption spectra as well as electrochemical and photovoltaic properties of these polymers were investigated systematically. Some units exhibiting the same effect of band-zip lowering exhibited different effects on molecular energy levels of the polymers. For example, the TPZ unit can reduce the bandgap by lowering the LUMO energy level and elevating the HOMO level of the polymer, but the BT unit can lower the bandgap only by depressing the LUMO level. Since open-circuit voltage (V-oc) of the heterojunction polymer solar cell is believed to be inversely proportional to the HOMO level of electron donor material, V,, of the devices based on H9, the copolymer of BDT and TPZ, was ca. 0.5 V lower than that of the device based on H7, the copolymer of BDT and BT. The effects of seven commonly used units on bandgap, molecular energy level, and photovoltaic properties of the BDT based polymers are studied and discussed in this paper, which can provide a guideline not only for design of photovoltaic materials but also for materials of various other electronic devices. In addition, the PCE of the device based on PCBM and H6, one of the BDT-based polymers, reached 1.6%, and V-oc, I-sc, and FF of the device were 0.75 V, 3.8 mA/cm(2), and 56%, respectively, which indicates that BDT is a promising common unit for photovoltaic conjugated polymers. Since we have developed the synthetic method of the 4,8-bisalkoxy-BDT monomer, the BDT unit will play an important role in future research on conjugated polymer design.