Synthesis And Research On Perylene Imides Electron Acceptors

Perylene imides, as one of the most common non-fullerene electron acceptor materials, have attracted considerable attention because of excellent optical properties, high molar extinction coefficient, thermal stability, high electronic mobility and modifiable chemical structures. However, due to the strong aggregation, perylene imides tend to form large crystalline aggregate domains, which are harmful to the excition dissociation and result in lower power conversion efficiency (PCE) of organic solar cells (OSCs). Fortunately, it is proved that non-planar twisted structure is an efficient way to restrict the crystallinity.Perylene monoimides (PMI), an indispensable member of perylene imides family, similar chemical properties with perylene diimides (PDI), have not been studied systematically in BHJ OSCs. Compared to PDI, PMI derivatives own a higher LUMO energy level because of the less imide-ring, that is beneficial to get higher open circuit voltage. Thus, we believe that PMI derivatives are potential electron acceptor materials. Based on the above two reasons, we have designed and synthesized a series of non-planar perylene imides molecules, and characterized their optical and electrical properties.1. Two novel molecules 21 and 2O with twisted structures based on PDI were designed and synthesized. In dichloromethane, λabs values of the two molecules are 540nm and 529,and λcm values are 549nm and 582nm. Both of molecules have stronger absorption capacity than a single molecular of PDI. LUMO energy levels of them are 3.89eV and 3.83eV, similar to PCBM. In particular, molar extinction coefficient of 20 in dichloromethane can reach 2.13×105, fluorescence quantum yield is 0.66. Both 21 and 20 are potentially good electron acceptor materials.2. Three new twisted and star-shaped molecules with PMI as branches and pyrene, triphenylamine,truxene as core were designed and synthesized respectively.All the molecules have strong absorption. λabs values of the three compounds are 520,525,525nm and λcm values are 574,638,580nm. Molecular extinction coefficient of all the molecules in dichloromethane is more than 105, LUMO energy levels are around 3.5 eV,0.4 eV higher than that of the PDI. Using them to blend with P3HT to fabricate solar cell devices, all of them can get high Voc. The Voc of 3H,31 and 3J is 0.90,0.71,0.99V respectively.3. A series of PMI-F molecules were synthesized using different PMI with different side chains on N atom and different fluorene wtin different side chains on 9,9 potition.The different side chains have little influence on absorption characteristics and LUMO energy level. λabs values are all around 525nm and LUMO levels are all around 3.5eV. There is a great difference between different molecules and 4J2 can get the highest PCE of 1.02%. The reason why PCE values of solar cells devices using defferent molecules have so great difference is that side chains have great impact on morphology of organic activity layer film.