中文摘要：

我们将Bis-PC_（70）BM作为第二种电子受体混入基于PTB7：PC_（70）BM的聚合物太阳能电池中,制备了三元混合聚合物太阳能电池.相比于PC_（70）BM,Bis-PC_（70）BM的最低未占分子轨道（lowest unoccupied molecular orbital,LUMO）能级更高,所以掺入Bis-PC_（70）BM后器件的开路电压（V_（oc））得到了提升.Bis-PC_（70）BM在PTB7和PC_（70）BM之间起到桥梁的作用,因此在给体/受体界面创造了更多的电荷传递通道.而且从原子力显微镜中得到的结果来看,当混入质量比为3%的Bis-PC_（70）BM后薄膜的表面形貌更为平整,平均粗糙度从原来的1.87 nm降到了1.80 nm.能量转换效率（power conversion efficiency,PCE）达到7.00%,其中器件的V_（OC）为0.77 V,短路电流（J_（SC））为13.92 mA·cm^（-2）,比PTB7：PC_（70）BM的器件效率6.07%提高了15%.

英文摘要：

In recent years, solar cells, especially the bulk heterojunction （BHJ） polymer solar cells （PSCs）, have attracted considerable attention. BHJ PSCs have several advantages such as easy fabrication, light weight, low cost and flexibility. The research on ternary BHJ PSCs will become a hot topic since incorporating near infrared region （NIR） low bandgap polymer materials into the donor/acceptor system can easily extend the absorption spectral range and improve the photon harvesting. In this paper, we investigate the ternary PSCs based on poly{4, 8-bis[（2-ethylhexyl）-oxy]benzo[1, 2-b ： 4, 5-b＇]dithiophene-2, 6-diyl-alt-3-fluoro-2-[（2-ethylhexyl） carbonyl]thieno[3, 4-b]thiophene-4, 6-diyl} （PTB7）： Bis adduct of phenyl-C71-butyric acid methyl ester （Bis-PCToBM）： [6, 6]-phenyl-C71-butyric-acid-methyl-ester （PC70BM）. The performance of PSCs based on PTB7 and PCToBM may be improved by doping with Bis-PCToBM which is used as an electron-cascade acceptor material. Ternary blend PSCs with 3% Bis-PCToBM exhibit a power conversion efficiency （PCE） of 7.00%, higher than that （6.07%） of the PTB7 ：PCToBM binary blend. The open-circuit voltage （Voc） is 0.77 V, the short-circuit current （Jsc） is 13.92 mA.cm-2 and the fill factor （FF） is 65%. However, in our research, the absorption spectra for the films with different amount of Bis-PCToBM are hardly changed, implying that doping with Bis-PCToBM would not improve the photon harvesting. The LUMO （HOMO） energy levels of PTB7, Bis-PCv0BM and PCToBM are -3.49 eV （-5.31 eV）, -3.80 eV （-6.10 eV） and-3.91 eV （-6.20 eV）, respectively. Due to the higher LUMO energy levels of Bis-PCToBM relative to PCToBM, the Voc increases when Bis-PC~0BM is used. The cascade-like energy levels of ternary blend PSCs can facilitate the charge transfer at the donor/acceptor interface owing to the bridging effect. There are three routes for charge transfer （PTB7-Bis-PC70BM, Bis-PC70BM-PC70BM and PTBT-PC70BM） in ternary PSCs, more