Design,Synthesis And Properties Of Nonfullerene Acceptor Materials For Organic Photovoltaic

Four novel small molecule acceptors based on the excellent acceptor FDICTF?F-H?reported in our group were designed and synthesized.F-TT-2F was designd with a thieno[3,4-b]thiophene?TbT?as bridge between the donor and acceptor moieties,and introduced two fluorine atoms onto its acceptor moiety,to enhance the ICT effect.F-F,F-Cl and F-Br were designed with a halogenation strategy on FDICTF?F-H?.Their chemical structures,thermal stability,optical/electrochemical properties,morphology of active layer and photovoltaic performance were investigated.The details were as follows:Firstly,three non-fullerene acceptors F-F,F-Cl and F-Br were designed and synthesized by introducing halogenation atoms F,Cl and Br onto the end group of the acceptor FDICTF?F-H?.Compared with F-H,the three small molecules show red-shifted absorptions,increased crystallinities and higher charge mobilities.After blending with PBDB-T,the devices of F-F,F-Cl and F-Br exhibit PCEs of 10.85%,11.47%and 12.05%,respectively.The results are higher than the device of F-H?9.59%?.It is worthy to note that the PCE of 12.05%for F-Br based device is one of the highest PCEs of a few single-junction organic photovoltaic devices with efficiencies over 12%reported at that time.Secondly,F-TT-2F was designed and synthesized based on the acceptor FDICTF?F-H?,with a ester-substituted thieno[3,4-b]thiophene?TbT?and two fluorine atoms onto its D and A moieties.Thieno[3,4-b]thiophene?TbT?has a significant quinoid-enhancing effect and two fluorine atoms substituted end group has strong electron-withdrawing ability,which can decrease the highest occupied molecular orbital?HOMO?and lowest unoccupied molecular orbital?LUMO?energy levels and enhance intramolecular charge transfer.F-TT-2F shows a much red-shifted absorption in contrast to the above three molecules.By combining with PTB7-Th,the PCE is up to 9.14%with very high J_scc values of 19.24 mA cm^-2.Although the PCE was lower than FDICTF based device?10.06%?,the obvious red-shifted absorption was obtained.The strategy used herein could be employed to design molecules with wide absorption windows and to boost higher efficiency for organic solar cells.