Small Molecule Acceptor Materials Based On Indacenodithiophene And Indacenodiselenophene As Electron-Donating Core

In recent years,the acceptor-donor-acceptor(A-D-A)type non-fullerene small molecule acceptor(NF-SMAs)with electron-rich fused rings as the central unites have received more and more attention.The chemical features of these NF-SMAs include:(1)a modular structure,consisting of an electron-rich core,electron withdrawing end groups,?-bridges,and side chains,which benefits molecular tailoring;(2)facile synthesis,purification,and scalability.The electron-rich fused rings could improve the?-?stacking among molecules and facilitate the extension of light absorption.Howeover,the large coplanar nonfullerene SMAs having much strong?-?stacking may decrease the solubility in organic solvents and compatibility with polymer donors in active layer,resulting in large separation in the morphology of blend films and inferior photovoltaic performance.In order to solve the problem,five A-D-D-A types NF-SMAs were designed and synthesized,and the photovoltaic properties of these five acceptor materials were studied in detail.The main research contents are as follows:1.Two A-D-D-A types NF-SMAs IDT2-IC and IDT2-IC-4Cl were designed,in which indacenodithiophene(IDT)used as the electron-rich core and 3-(Dicyanomethylidene)indan-1-one(IC)and 2-(5,6-dichloro-2,3-dihydro-3-oxo-1H-inden-1-ylidene)(IC-2Cl)as the end groups.Compared with IDT2-IC,IDT2-IC-4Cl has a low optical band gap of 1.40 e V,a wide absorption region at 450-900 nm,and stronger molecular aggregation and crystallinity.The PBDB-T:IDT2-IC-4Cl-based device shows a photoelectric conversion efficiency(PCE)of 12.53%with a short circuit current(J_sc)of 22.22 m A cm^-2 and a fill factor(FF)of 69.81%,while the PBDB-T:IDT2-IC-based device shows a PCE of 8.17%with a J_sc of 13.23 m A cm^-2 and a FF of 65.71%.Our study provides an effective molecular design strategy for the construction of more effective NF-SMAs.2.Three A-D-D-A types NF-SMAs C6PhIDSe2-IC,C6PhIDSe2-IC-4Cl and C6PhIDSe2-IC-4F using indacenoselenophene(IDSe)as electron-rich fused ring central core,IC,IC-2Cl or 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile(IC-2F)as electron-deficient end groups.In this chapter,the use of selenium,is to improve the orbital overlap,and increase the ground state molecules quinoid resonance characteristics.Relative to IDT acceptor materials,Three A-D-D-A type NF-SMAs C6PhIDSe2-IC,C6PhIDSe2-IC-4Cl and C6PhIDSe2-IC-4F had wider absorption in the range of 450-900 nm,and more balanced charge mobility was obtained based on PBDB-T:C6PhIDSe2-IC-4F.The PBDB-T:C6PhIDSe2-IC-4F-based device,PBDB-T:C6PhIDSe2-IC-4Cl and PBDB-T:C6PhIDSe2-IC shows a PCE of 9.02%,7.07%and 5.68%,respectively.This study provides a feasible optimization strategy for further regulating the material's spectral absorption,energy level and charge transfer.