Design,synthesis And Characterizations Of Non-fullerene Acceptors Based On Intramolecular Non-covalent Interactions

Non-fullerene acceptors have been widely studied due to their wide material sources,easily adjusted molecular structures and energy levels.Organic solar cells based on non-fullerene acceptors have reached power conversion efficiency of above18%.Cost and device stability still hold back the commercialization of organic solar cells.The traditional fused-ring non-fullerene acceptors usually contain a large fused molecular backbone which would lead to more difficult synthesis and higher cost.Also,more fused rings will decrease molecular solubility which brings problem in purification and device fabrication.While in non-fused non-fullerene acceptors,the building blocks are linked through single bonds avoiding annulation actions,which could efficiently lower cost.The non-covalent interactions between adjacent units provide non-fused acceptors planar backbones which could lead to good molecular packing and charge transport property.In this thesis,we designed and synthesized novel non-fused non-fullerene acceptors.The relationship between molecular structural adjustment and device performance has been studied by organic solar cell investigation.The molecular charge mobility and device performance could be tuned by introducing different functional groups.The contents of this thesis are listed below.1.Two A-D-A’-D-A type non-fused acceptors,namely,BT-F and BT-Cl,composing of benzo[c][1,2,5]thiadiazole（BT）,cyclopenta[2,1-b:3,4-b’]dithiophene（CPDT）and 2-（5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene）malononitrile（IC–2F）or 2-（5,6-dichloro-3-oxo-2,3-dihydro-1H-inden-1-ylidene）malononitrile（IC–2Cl）were designed and synthesized.The photovoltaic properties of BT-F and BT-Cl were systematically investigated utilizing organic solar cell devices.The N···S and O···S interactions between BT,CPDT and IC units make BT-F and BT-Cl possessing planar backbones.Easily accessible donor material PTQ-10 was used to further reduce cost.Devices based on PTQ-10:BT-F afforded optimal PCE of 8.26%.The Cl atoms in BT-Cl enhanced molecular photon harvesting and electron mobility.Hence,devices based on PTQ-10:BT-Cl provided better PCE of 8.65%.Devices based on PTQ-10:BT-F and PTQ-10:BT-Cl exhibited low voltage loss of 0.57 V and0.59 V,respectively,which implying balanced J_sc and V_oc.The devices showed good stability stored in air without encapsulation.This work showed a good example for construction of low cost,stable and commercialized organic solar cells.2.Designed and synthesized two non-fused acceptor FTh-IC4Cl and Cl Th-IC4Cl composed of halogenated thiophene,CPDT and IC-2Cl units.The photovoltaic properties of FTh-IC4Cl and Cl Th-IC4Cl were systematically investigated utilizing organic solar cell devices.Halogen atoms can adjust energy levels of FTh-IC4Cl and Cl Th-IC4Cl.Halogen atoms could also form non-covalent interactions affording FTh-IC4Cl and Cl Th-IC4Cl with planar molecular conformation.The organic solar cell devices based on J52:FTh-IC4Cl using SHNa as additive afforded better performance with PCE of 4.02%.ODT was a more suitable additive for J52:Cl Th-IC4Cl system providing PCE of 4.37%.J52:Cl Th-IC4Cl exhibited better photovoltaic properties than J52:FTh-IC4Cl blend films.3.Two A-D-A’-D-A type non-fused acceptors（ROBT-F and ROBT-Cl）based on multiple O···S non-covalent interactions have been designed and studied utilizing theoretical calculation.The intermediate molecules have been synthesized and identified.Multiple O···S non-covalent interactions between adjacent units lead to small torsion angle in molecular backbones.Molecule with chloro end groups exhibited lower energy levels and bandgap than that with fluoro end groups.4.A series of anthanthrene derivatives abbreviated as A-OC8,BT-A-BT,Na-A-Na and Az-A-Az have been design and synthesized.Charge mobilities of these molecules were studied by organic field-effect transistor investigation.Energy levels and molecular packing could be tuned utilizing functional groups.Az-A-Az showed much smaller torsion angle between anthanthrene core and functional groups than those of Na-A-Na and BT-A-BT.Az-A-Az also exhibited narrowest bandgap among these anthanthrene derivatives.Organic field-effect transistor devices based on A-OC8 showed maximum hole mobility of 0.026 cm~2 V^-1 s^-1.After introducing benzothiophene units,the device performance based on BT-A-BT decreased to7.58×10^-4cm~2 V^-1 s^-1.When substituted with naphthalene units,the mobility increased up to 0.078 cm~2 V^-1 s^-1.In the case of Az-A-Az,the highest mobility of0.13 cm~2 V^-1 s^-1 was obtained.The results indicate that azulene can efficiently tune energy levels and molecular packing.Azulene is proved to be an important building block for constructing high performance organic semiconductors.