Synthesis And Photovoltaic Properties Of Novel C-O Bridge Accepteor Small Molecules

Since Alan Heeger laboratory reported bulk-heterojunction organic solar cells in 1995,Organic solar cells are widely concerned by many scientists for their light weight,flexibility and translucency.The active layer of OSCs generally consists of the electron donor and the electron acceptor.Donor materials mainly contains polymer donor material and small molecules donor materials,acceptor materials mainly contains fullerenes acceptors and nonfullerene acceptors,the fullenerene acceptor has developed many years for their good electron mobility and their suitable miscibility with donors.But poor light-harvesting capability,low tunability of energy levels and poor stability for fullerenes limit further improvement in PCE.In recent years,with the emergence of non-fullerene receptors,especially the development of Acceptor–donor–acceptor?A-D-A?ladder-type fused ring acceptor materials,these problems have been effectively solved.The efficiency of organic solar cells has been constantly updated.The efficiency of single-junction solar cells has reached 15%,and that of tandem solar cells has reached 17%.In this paper,we synthesized several novel CO-bridge trapezoidal fused ring small molecule Acceptors,and discussed the photovoltaic performance.This paper mainly involves two aspects of research:?1?A-D-A nonfullerene acceptor CO_i7IC and CO_i7DFIC were obtained by taking CO_i7,A seven-ring unit,as the core,IC and DFIC as the terminal group,respectively.The donor was PTB7-Th,through the optimization of D/A ratio,thickness and additives,the power conversion efficiency of the cells were 6.36%and 8.32%,respectively.Then we tested the photovoltaic properties and morphology of the cells to confirm the effect of fluorine.In addition,the structure of CO_i7IC was also confirmed by the single crystal XRD analysis,which is quite different from those of C-bridged A-D-A NFAs.?2?According to the previously reported CO5IC,CO5DFIC was synthesized after the end group was changed into DFIC,CO5DFIC-OT and CO5DFIC-ST was synthesized by adding alkoxythiophene?OT?and alkylthiothiophene?ST??-bridges.Then compared their Optical and electrochemical properties,and made devices with the donor PTB7-Th.Compared with CO5DFIC,CO5DFIC-OT and CO5DFIC-ST have higher lowest unoccupied molecular orbital?LUMO?levels and better light-harvesting capability,thus enhancing the open circuit voltage(V_oc),short-circuit current density(J_sc)and power conversation efficiency?PCE?for solar cells.