Design,Synthesis,and Photovoltaic Application Of Perylene Diimides Electron Acceptors

In the past decade,organic solar cells have developed rapidly because of their flexible and light-weight properties.However,the instablility and high cost of high performance materials hinder their commercial process applications.Perylene diimide（PDI）derivatives as old excellent semiconductors have the advantages of thermal stability and strong visible light absorption.They could be used as acceptor materials in organic solar cells.This type materials suffer from the strong tendency to aggregate and narrow absorption ranges.In this study,a series of new small molecules and polymer acceptors based on PDIs.They were applied in the bulk-heterojunction organic solar cells（BHJ OSCs）successfully.It is divided into the following two parts.1.A series of benzodiperylene diimides polymers（P（TBDPDI-TT）,P（TBDPDI-FTT）,P（TBDPDI-EDOT））were designed and synthesized.The twisted benzodiperylenediimides（TBDPDI）with large conjugated structure and three-dimensional spatial configuration were synthesized from 3,4,9,10-perylenetetracarboxylic through reaction of hydrolysis,bromination,Suzuki coupling et al.In order to balance the carrier transmission and exciton dissociation,combined with the design principles of small molecules and polymer acceptors,three twisted benzoimide polymers（P（TBDPDI-TT）,P（TBDPDIFTT）,P（TBDPDI-EDOT））were obtained through bromination and polymerization of TBDPDI.All compounds show strong absorption in 300～700 nm,deep lowest unoccupied molecular orbitals of-3.70～-3.80 e V,decomposing temperature higher than 375^oC.Bulk heterojunction solar cells based on acceptor P（TBDPDI-TT）reached power conversion efficiency of 5.69%.2.A series of perylene diimides derivatives（PDIs）with near-infrared（NIR）absorption and different geometries were synthesized by introducing 4-phenyl-1,2,4-triazoline-3,5-dione（PTAD）and 4-butyl-1,2,4-triazoline-3,5-dione（Bu TAD）to the bay position of PDIs through the Diels–Alder reaction.The compounds with various twisted three-dimensional（3D）structures were obtained through combining different connection units,and their aggregation and domain size of the donor-acceptor blends were adjusted.All of these compounds exhibit broad absorption in the range of 300～860 nm,high thermal stability（with a decomposition temperature over 350°C）,applicable lowest unoccupied molecular orbital energy levels（-3.70～-3.74 e V）,and appropriate solubility.Blending with a PM6 polymer donor,bulk hetero junction organic solar cells（BHJ OSCs）based on BDT-SBu TADPDI₂exhibited the highest power conversion efficiency of 2.74%.Their carrier mobility and morphology were investigated by Space-charge-limited current（SCLC）measurements and Atomic Force Microscopy（AFM）measurements respectively.This study provides a promising strategy to construct potential PDI-based acceptors with NIR absorption.