Synthesis And Photovoltaic Properties Of Fused-ring Electron Acceptor Materials Based On BTBT

In recent,years,due to the easily modified molecular structure,good thermodynamics and optical properties,fused-ring electron acceptor(FREAs)has attracted wide atrtention from researchers.FREAs,an emerging branch of the non-fullerene organic solar cell(NF-OSCs),has made an unprecedented breakthrough,with the energy conversion efficiency(PCE)of the single devices exceeding 18%.In this disseitation,some latest research papers of FREAs materials in bulk heterejunction(BHJ)solar cells(OSCs)have been reviewed,and comprehensively understand the relationship of the stmcture and performance from the structural characteristics of FREAs materials.By considering the structuras characteristics of BTBT and FREAs materials,five small molecular receptor materials containing BTBT were designed and synthesized.The main contents of this dissertation are as follows:(1)The three isomeric FREAs with the octacyclic electrorn-donating core(D)of benzo[b]benzo[4,5]thieno[2,3-d]thiophene(BTBT)fused with diarylcydopentadieny-Ithiophene and electr on-deficient 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malonontrile(2FIC)as terminals(A)were designed and synthesized,where the cyclopentadienyl moiety was fused at the 2,3-7,8(Z1-aa),2,3-6,7(Z1-ab),and 1,2-6,7(Z1-bb)positions of the benzo[b]benzo[4,5]thieno[2,3-d]thiophene(BTBT)-based fused-ring cores.The effects of the three small molecules acceptors by cyclizing at different condensation sites on the photoelectric properties,photovoltaic properties and morphology of FREAs were discussed in detail.The results show that the core of fiised-ring formed by different condensation sites plays a key role to improve the performance for FREAs based devices.All three isomers lave well matching with energy levels of the polymer dotor PM6,and all have high VOC(0.98?1.00 V).Compared with Z1-aa and Z1-ab,Z1-bb has a wider redshift absorption spectrum and a bigger molar extinction coefficient.When it is blended with PM6,compared with PM6:Z1-aa and PM6:Z1-ab blend membranes:PM6:Z1-bb blends have more dominant face-on stacking,better blend morphology and more balance charge mobility.Thus,PM6:Z1-bb based OSCs devices obtained high Jsc(18.52 mA cm-2),VOC(0.98 V),and FF(70.05%),resulting in the highest PCE value of 11.66%(2)The three new FREAs with the octacyclic electron-donating core(D)of benzo[b]benzo[4,5]thieno[2,3-d]thiophene(BTBT)fused with diarylcyclopentadienylthiophene and two different electron-deficient group(2-(5,6-dichloro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile(2C1IC)and the mixture of 2-(5-chloro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile and 2-(6-chloro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile(1C1IC)as terminals(A)were designed and synthesized.The effects of different end groups on photoelectric properties:photovoltaic properties and morphology of FREAs were studied.The results showed that both.two small molecules possess wide absorption in the range of 500-850 nm,and BTIC-2C1 possesses the higher molar absorption coefficient.For the neat film of two small molecules;the absorption of BTIC-1C1 is wider,and its solubility is better than that of BTIC-2C1,which is conducive to forming a good phase separation and phase purity with the donor PM6,so the PM6:BTIC-1C1 based OSCs devices obtained high JSC(18.40 mA cm-2)and FF(69.55%),and finally present the best PCE of 12.66%.