Rui Yang, Xuediao Cai, Liming Ding
2015
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Journal
Acta Chimica Sinica
Abstract
Due to poorly solubility of the fused ring compound 4,10-dibromoanthanthrone (VAT Orange 3) in common organic solvents, its application as optoelectronic material was hindered. Here, the soluble compound 4,10-bis(4-hexyl-2-thienyl)-6,12-bis(dicyanovinylene)dihydroanthanthrene (TCVA) was successfully synthesized by introducing alkyl-thiophenyl and cyano groups into VAT Orange 3 compound by Still coupling and Knoevenagel reaction. The properties of TCVA were investigated. The UV-vis spec-trum indicated that TCVA showed strong absorbance in the solar spectrum. The TCVA exhibited lower LUMO energy level ( - 4.42 eV), which was comparable with fullerene acceptor material PCBM ( - 4.2 eV). The solar cell device ITO/ZnO/P3HT:TCVA/MoO 3 /Ag based on TCVA as acceptor and P3HT as donor material was fabricated. The power conversion efficiency (PCE) of 0.3% was achieved for acceptor TCVA with open-circuit voltage ( V oc ) of 0.22 V, short circuit current ( J sc ) of 3.61 mA•cm - 2 and fill factor ( FF ) of 37%. The solar cell based on TCVA achieved lower efficiency, maybe due to the lower LUMO energy level of TCVA and small difference of energy level (0.75 eV) between P3HT HOMO and TCVA LUMO. A lower LUMO energy level may lead to a lower open circuit voltage ( V oc ), since V oc is proportional to the energy level difference between the donor HOMO and acceptor LUMO. The donor polymer ploy[4,10-bis(4-hexyl-5-bromine-2-thienyl)-6,12-bis(dicyanovinylene)dihydroanthanthrene]-alt-2,6-bis(trimethyltin)-4,4-bis(2-ethylhexyl) two-thieno[3,2-b:2',3'- d ]silole (PTCVADTS) with TCVA as the acceptor unit were synthesized and characterized. The polymer PTCVADTS showed good light-absorption properties, thermal stability, deep HOMO level ( - 5.33 eV), and low band gap (0.94 eV). Solar cell device ITO/PEDOT:PSS/ PTCVADTS:PC 61 BM/Ca/Al based on PTCVADTS as donor achieved an open-circuit voltage of 0.31 V and PCE of 0.018%. Compared with the LUMO level of acceptor ( - 4.2 eV), the lower LUMO level of donor ( - 4.39 eV) hindered the electron transport from donor to acceptor, which resulted in lower efficiency. Vat Orange 3 with large flat structure can expand conjugated system, which broadens the absorption. Further reducing the number of cyano group or introducing of other weaker electron withdrawing group may get results applauded.