以三聚茚为核的星型电子受体材料的合成、 表征与光伏性能

以高度平面共轭的烷基取代三聚茚为中心核, 以噻吩基团桥联, 在末端连接氰基茚酮作为拉电子基团, 设计合成了一类星型受体分子2,2',2″-{[(5,5,10,10,15,15-己基-10,15-二氢-5H-二茚[1,2-a：1',2'-c]芴-2,7,12-三基)三(噻吩-5,2-二基)]三(亚甲基)}三(3-氧杂-2,3-二氢-1H-茚-2,1-二叉)三丙二腈(NFT-C6)和2,2',2″-{[(5,5,10,10,15,15-癸基-10,15-二氢-5H-二茚[1,2-a：1',2'-c]芴-2,7,12-三基)三(噻吩-5,2-二基)]三(亚甲基)}三(3-氧杂-2,3-二氢-1H-茚-2,1-二叉)三丙二腈(NFT-C10). NFT-C6和NFT-C10的最高占据轨道(HOMO)和最低未占轨道(LUMO)分别位于-5.66和-3.75 eV. 其薄膜在400~700 nm范围内具有较大的吸收强度, 最大吸收峰分别位于606和586 nm. 以聚[(2,6-{4,8-二[5-(2-乙基己基)噻吩-2-基]-苯并[1,2-b：4,5-b']二噻吩})-{5,5-(1',3'-二-2-噻吩基-5',7'-二(2-乙基己基)苯并[1',2'-c：4',5'-c']二噻吩-4,8-二酮)}](PBDB-T)为给体材料, 以NFT-C6或NFT-C10为受体材料制备了太阳能电池器件, 器件在300~700 nm之间具有较宽的响应光谱, 其光电转换效率(PCE)分别达到1.09%和5.23%. 原子力显微镜(AFM)结果表明, PBDB-T和NFT-C10共混制备的光伏器件活性层具有合适的相分离尺寸, 有利于激子的有效解离, 而PBDB-T: NFT-C6器件的活性层相分离尺寸过大, 增加了激子复合的几率, 使器件的短路电流、 填充因子和PCE降低. 研究结果表明, 基于三聚茚的星型光伏材料具有一定的应用前景.

Synthesis,Characterization and Photovoltaic Properties of Truxene Based Star-Shaped Non-Fullerene Acceptors†

Small molecular non-fullerene acceptors(NFAs) have recently drawn tremendous attention. In this work, a class of star-shaped NFAs, namely 2,2',2″-{[(5,5,10,10,15,15-hexahexyl-10,15-dihydro-5H-diindeno[1,2-a：1',2'-c]fluorene-2,7,12-triyl)tris(thiophene-5,2-diyl)]tris(methanylylidene)}tris(3-oxo-2,3-dihydro-1H-indene-2,1-diylidene)trimalononitrile(NFT-C6) and 2,2',2″-{[(5,5,10,10,15,15-hexadecyl-10,15-dihydro-5H-diindeno[1,2-a：1',2'-c]fluorene-2,7,12-triyl)tris(thiophene-5,2-diyl)]tris(methanylylidene)}tris(3-oxo-2,3-dihydro-1H-indene-2,1-diylidene)trimalononitrile(NFT-C10), have been designed and synthesized by an alkyl-substituted truxene as the central group and three strong electron withdrawing cyano-1,3-indanone as the terminal groups. The highest occupied molecular orbital(HOMO) and lowest unoccupied molecular orbital(LUMO) energy levels of the compounds both lies at -5.66 and -3.75 eV, respectively. The NFT-C6 and NFT-C10 films show intense absorption from 400 nm to 700 nm with a maximum at 606 and 586 nm, respectively. The polymer solar cells(PSCs) devices using (PBDB-T=poly{[(2,6-{4,8-bis[5-(2-ethylhexyl)thiophen-2-yl]-benzo[1,2-b：4,5-b']dithiophene})-alt-{5,5-[1',3'-di-2-thienyl-5',7'-bis(2-ethylhexyl)benzo[1',2'-c：4',5'-c']dithiophene-4,8-dione]})(PBDB-T) as a donor, and NFT-C6 or NFT-C10 as an acceptor have been fabricated, which shows a power conversion efficiency(PCE) of 1.09% and 5.23%, respectively. The external quantum efficiency(EQE) spectra indicated broad photocurrent response from 300 nm to 700 nm of the devices. The aggregation properties of the device have been investigated by atomic force microscopy(AFM). The height and phase images of the active layers indicated that the PBDB-T： NFT-C10 based film showed proper phase separation with dozens of nanometers, which was benefit to exciton dissociation and produced desired device performance. On the other hand, the low short-circuit current density, fill factor and PCE of the ITO/ZnO/PBDB-T：NFT-C6/MoO₃/Ag photovoltaic device was attributed to the overlarge phase separation size between the donor and the acceptor. These results demonstrated that truxene based star-shaped NFAs have promising application in PSCs devices.