Design,Fabrication And Properties Of Novel Perylene Bisimide Organic Semiconductor Materials

With the development of the material science,organic semiconductor materials(OSMs)have attracted a lot of attention owing to their low cost,flexibility.Perylene bisimide derivatives(PBIs),as the n-type organic semiconductor,have wide application in color liquid crystal display(LCD),organic solar cells(OSCs),organic field-effect transistor(OFET)and so on.However,PBIs with a larger ?-conjugate plane and strong intermolecular interaction might lead to poor solubility and large microscale aggregates,thereby limits its application.So it has important practical significance to carry out certening on crystallization behavior and properties for PBIs.In this dissertation,we characterized crystallization behavior and non-fullerene all-small-molecule organic solar cells based on several PBIs acceptor.The main results are as follows:1.Select a series of long alkyl chain replaced perylene bisimide(C18-4ClPBI,C16-4ClPBI,C14-4ClPBI and C12-4ClPBI),and the thermodynamics,photoelectric properties and phase transition properties were characterized.The phase behavior and related structural evolution of lengthy alkyl substituted core-tetrachlorinated perylene bisimide(C18-4ClPBI)have been studied.It was found that the C18-4ClPBI can exist in liquid crystalline and crystalline phases depending on temperature,which transform reversibly between heating and cooling processes.X-ray diffraction results demonstrate that the C18-4ClPBI molecules both in crystalline and liquid crystalline phases can be well accouted for a monoclinic unit cell with varied cell parameters.This indicates that the liquid crystalline of C18-4ClPBI possesses a highly ordered structure in three dimensions.During liquid crystalline to crystalline phase transition,non-birefringent convex objects were observed,which disassembled in the reverse crystalline to liquid crystalline phase transition.The formation of the convex objects are attributed to the regions where the crystallization of C18-4ClPBI is prohibited.It was confirmed that the existence of the non-crystallizing convex objects results in a remarkable decrease of the electron mobilities from 1.51 × 10-3 cm2 V-1 s-1 in the liquid crystalline phase to 2.67 × 10-4 cm2 V-1 s-1 in crystalline phase.2.Two twisted singly-linked perylene bisimide(PBI)dimers with chalcogen bridges in the PBI cores,named as C4,4-SdiPBI-S and C4,4-SdiPBI-Se,were synthesized as acceptors for non-fiullerene all-small-molecule organic solar cells(NF all-SMSCs).A moderate-bandgap small molecule DR3TBDTT used as the electron donor displayed complementary absorption with C4,4-SdiPBI-S and C4,4-SdiPBI-Se.It was found that solvent-vapor annealing(SVA)played a critical role on photovoltaic performance in NF all-SMSCs,which improves the crystallinity.of donor and acceptors,promotes the proper phase segregation domain size and therefore enhances the charge transport.The PCEs of NF all-SMSCs devices based on DR3TBDTT:C4,4-SdiPBI-S and DR3TBDTT:C4,4-SdiPBI-Se increased from 2.52%to 5.81%and 2.65%to 6.22%,respectively,after exposure to chloroform vapor.The best efficiency of 6.22%is one of the highest PCEs for NF all-SMSCs based PBI acceptor so far.3.We synthesized a series of two twisted single bond PBIs as a nonfullerene accecptor in NF all-SMSCs,named Cn,n-SdiPBI-S(n=3,4,5,6,7),selecting a complementary and the moderate-bandgap small molecule DR3TBDTT as a donor.We found that the solvent annealing lead to different performance improvement with different alkyl chain perylene bisimide based NF all-SMSCs,which significant increase from around 2.5 times to 1.2 times.Considering the odd-even effect of organic molecules,we chose the odd alkyl chain perylene bisimide to study the reasons of the different performance change before and after annealing.In conclusion,with the increase of alkyl chain,the blend film phase size gradually increased,and excessive phase size hindered the further increase of the efficiency.4.We choose a series of different linked-position diPBI,named as B-SdiPBI,O-SdiPBI and H-SdiPBI.We systematically explore B-SdiPBI,O-SdiPBI and H-SdiPBI to recognize the relationship of molecular geometry on morphology and photovoltaic properties.The torsion angle between the two PBI units of B-SdiPBI is 67°.Owing to the large steric repulsion,the dihedral angle are increase to 86° and 90° for O-SdiPBI and H-SdiPBI.The molecular twisted and the PBI subunits planarity of the three molecules conform the following order:H-SdiPBI>O-SdiPBI>B-SdiPBI,and the performance of NF all-SMSCs also conform the following order:H-SdiPBI>O-SdiPBI>B-SdiPBI,suggesting that the molecular conformations of the single-linked diPBI derivatives are delicately tuned by the performance of NF all-SMSCs.