Synthesis Of New Fused-Ring Small-Molecules And P-Type Polymers Containing Benzotriazole

Organic optoelectronic materials show potential applications and values in the fields such as organic solar cells,organic light-emitting diodes,sensors,organic thin-film transistors,and others because of their abundant resources,good flexibility,low costs,spectral tunability,and large-area preparation.Among them,organic solar cells are one of the most promising next-generation photovoltaic technologies for clean and renewable energy sources.It has attracted much attention in the past decades due to its advantages such as low cost,light-weight,solution processable,and large area printable preparations.The active layers of organic solar cells consist of donor materials and acceptor materials,and it is of great significance to design and synthesize novel donor and acceptor materials to improve the power conversion efficiencies of OSCs.Recently,due to the rapid development of the photovoltaic materials and device engineering,the power conversion efficiencies have exceeded 19%.In the development of the organic solar cells,the development of donor and acceptor materials are equally important,among which polymer donor materials constructed by electron-donating and electron-withdrawing units have been a major research interest in this field.The optical,electrochemical and photovoltaic properties can be modified by changing the structure of the electron-donating unit or the electron-withdrawing unit.Benzotriazole（BTA）is a weak electron-deficient unit,widely used in donor and acceptor materials because of the introduction of different alkyl chains on the nitrogen atom that can regulate the solubility of the materials and the morphology of the active layer.This thesis mainly designed and synthesized p-type polymers and fused-ring small-molecules based on the DA’D unit containing the benzotriazole group,to investigate the photovoltaic performance and luminescent properties.The following research results were obtained:1.A series of novel p-type polymers,BDT-TT,BDT-Se,BDD-TT,and BDD-Se,were designed and synthesized based on the DA’D fused-ring unit of benzotriazole.Fine-tuning on the absorption and bandgap of polymers were achieved through backbone selenophene and thiophene strategies.（1）The backbone selenophene strategy effectively reduces the bandgap.（2）The backbone thiophene strategy extends the absorption of the polymer and reduces the bandgap.（3）The synergistic effect of selenophene and thiophene strategies achieves the broadening and red-shifting of absorption,reducing the bandgap.Using PC₇₁BM and Y6 as the electron acceptor materials,the four polymers-based device gave an efficiency of 1～2%.2.The small-molecules BTA-EH and BTA-Bn with a fused ring structure were synthesized by using the central core unit of the dithienothiophene[3,2-b]pyrrolobenzotriazolyl DA’D as the fused-ring unit and with 2-ethylhexyl side chains on pyrrolo-N,followed by fusing the DA’D unit with 1,2-dichlorobenzene through two pyrrole rings to form new fused-ring conjugated backbones.Then on the ending pyrrolo-N sites,2-ethylhexyl and 3,4-dichlorobenzyl were decorated.The single crystal structure of BTA-EH confirms that the orthogonal side chains on the N atom of the DA’D pyrrolo-N sites have a certain steric hindrance effect,effectively reducing theπ-πstacking between molecules.In the solution,two molecules exhibited similar fluorescence lifetimes.In solid powders,the fluorescent lifetime of BTA-Bn is twice as long as that of BTA-EH（2.16 ns vs.0.89 ns）,and the corresponding fluorescent quantum yield is also twice as higher（8.8%vs.4.4%）.It can be seen that the aggregation induced quenching effect is effectively reduced through the synergistic effect of fused-ring structure and orthogonal side chains,and the use of bulk alkyl chain modifications on the ending pyrrolo-N can effectively regulate the fluorescent quantum yield and fluorescence lifetime.