He Youjun, Wang Xiang, Zhang Jing, Li Yongfang
Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China; Graduate University of Chinese Academy of Sciences, Beijing 100039, P. R. China.
Macromol Rapid Commun. 2009 Jan 2;30(1):45-51. doi: 10.1002/marc.200800507. Epub 2008 Nov 13.
Three low bandgap copolymers of thiophene and benzothiadiazole with electron-donating and electron-withdrawing substituents, P1, P2, and P3, have been synthesized by Pd-catalyzed Stille-coupling. Electronic energy levels of the polymers are estimated by cyclic voltammetry. The polymer films show a broad absorption band in the wavelength range from 300 to 750 nm. Among the polymers, the polymer that contains the 5,6-dinitrobenzothiadiazole unit, P3, possesses the smallest bandgap of 1.55 eV calculated from its absorption band-edge at ≈800 nm. With the increase of the electron-withdrawing ability of the substituents on the benzothiadiazole unit, the energy bandgap of the polymers decreased in the order P1 > P2 > P3. The results indicate that stronger electron-withdrawing substituents on the acceptor unit can effectively decrease the bandgap of the polymers.
通过钯催化的Stille偶联反应合成了三种具有供电子和吸电子取代基的噻吩与苯并噻二唑的低带隙共聚物P1、P2和P3。通过循环伏安法估算聚合物的电子能级。聚合物薄膜在300至750nm波长范围内呈现出宽吸收带。在这些聚合物中，含有5,6-二硝基苯并噻二唑单元的聚合物P3，根据其在≈800nm处的吸收带边缘计算，具有最小的带隙1.55eV。随着苯并噻二唑单元上取代基吸电子能力的增强，聚合物的能带隙按P1＞P2＞P3的顺序降低。结果表明，受体单元上更强的吸电子取代基可有效降低聚合物的带隙。
