Liquid-crystal-molecule Assisted Donor Materials Assembly for High-performance Organic Solar Cells
The optimization of the active layer morphology is the key to achieving efficient and stable bulk heterojunction organic solar cells(OSCs),and additive engineering is widely used to optimize the film morphology of the active layer in OSCs.A strategy is proposed to optimize the aggregation behavior of donor polymer(PM6)in blended films by using a simple liquid crystal molecule 4-cyano-4'-heptylbiphenyl(7-CB)as an additive.Through wide-angle X-ray scattering,in situ absorption spectroscopy and molecular dynamics simulation,it was found that 7-CB induced the regular arrangement of PM6 through the van der Waals force and CH/π interaction with the alkyl side chain of PM6,which enhanced the interaction between PM6 and PM6,and then enhanced the preaggregation of PM6 in solution,thus improving the crystallites of the active layer film.Benefit from this,charge transfer in the active layer film without any post-treatment is improved,and charge recombination is greatly suppressed.The power conversion efficiency of rigid and flexible binary OSCs prepared by PM6:L8-BO based on 7-CB treatment was increased from 15.41％and 14.90％to 18.01％and 17.26％,respectively.
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