| In recent years,organic solar cells(OSCs)have developed rapidly.At present,the highest power conversion efficiency(PCE)under laboratory conditions has exceeded18%,but there is still a long way to go before their commercial applications.The rapid improvement of their PCE is mainly attributed to the development of new non-fullerene acceptors and the utilization of high-performance polymer donors.Perylene diimide(PDI)-based organic semiconductor materials have good light and thermal stability and high electron mobility,making them excellent acceptors.In this paper,by designing and selecting PDI acceptor materials with different molecular configurations and containing different alkyl chains,organic solar cells were prepared through different conditions such as no solvent additives,sequential spin coating of active layers,and non-halogen solvent treatment.The relationship between the morphology and vertical phase separation structure of the active layers and the performance of the devices was systematically studied through characterization and testing.It includes the following three parts:(1)Seleno twisted benzodiperylenediimides(TBDPDI-Se)small molecular acceptors were designed and synthesized.Two side chains of 1-pentylhexyl(C11)and1-undecyldodecyl(C23)were used to adjust solubility and molecular packing.The twisted ladder-type conjugated structure effectively inhibits the aggregation and enhances the electronic coupling between the cores.The two acceptors have good thermal stability(Td>325 oC),the strong absorption at 300?600 nm.For TBDPDI-Se-C11,the maximum extinction coefficient(?)is 9.2×105 M-1 cm-1,and the highest electron mobility(?e)is 4.72×10-4 cm2 V-1 s-1.The lowest unoccupied molecular orbital(LUMO)energy levels of the two acceptors are-3.71 e V and-3.73 e V,respectively,which can be well-matched with many excellent donor polymers.Bulk heterojunction(BHJ)organic solar cells based on PBDB-T:TBDPDI-Se-C11 obtained a PCE of 6.37%without adding any additives and other post-treatments.After annealing at 100 oC for 10 minutes,the device efficiency increased to 7.41%.(2)Layer-by-Layer(LBL)solution-processed organic solar cells with three PDI small molecule acceptors.Through testing and analysis of different active layers,LBL active layers have different vertical component distribution and vertical phase separation structures with those of the BHJ active layers.In the LBL active layers,more acceptors are enriched on the surface of the active layer,while there is still good contact between the donor and the acceptor,and fewer defects in the active layers for higher Voc,Jsc,and FF.The LBL OSCs based on TBDPDI-C5,TBDPDI-C11,and Sdi PDI obtained PCEs of 6.11%,5.00%,and 3.60%,respectively,higher than 5.14%,4.82%,and 3.11%of BHJ OSCs.This is the first time that PDI small molecule acceptors are used to produce high-efficiency LBL OSCs.(3)Layer-by-Layer(LBL)solution-processed pseudo-planar heterojunction(PPHJ)OSCs with PDI polymer acceptors.Two polymer acceptors of P(4CF8CH-PDI-TT)and P(20CH-PDI-TT)with different alkyl chains and the low-toxic o-xylene were used to prepare the BHJ and PPHJ OSCs by using the difference in solubility of donor and acceptor.The semi-perfluoroalkyl chains have a better solubilizing effect when the chain length is shorter.P(4CF8CH-PDI-TT)containing semi-perfluoroalkyl chains has a high molecular weight of 94.8 k Da,good solubility,and high electron mobility.The PPHJ OSCs based on P(4CF8CH-PDI-TT)and P(20CH-PDI-TT)obtained PCEs of3.43%and 3.15%,respectively,which were higher than 1.71%and 1.10%of BHJ OSCs. |
PDF Full Text Request