Construction of Novel Polymers with Phenyl Substituted Benzodithio-phenedione for Photovoltaic Performance Study
Owing to the continuous development of materials and devices,the power conversion efficiency(PCE)of organic photovoltaics(OPV)has been improved continuously.However,there are some extra treatments used,which are not condu-cive to the large-scale production of OPV.Reasonably adjusting the solubility,crystallinity,and phase morphology of active layer could be of great importance to simplify processibility and directly obtain high-performance as-cast devices.In this work,a new phenyl substituted benzodithiophenedione unit(m-PhEh-BDD)was designed and synthesized through a facile selective acylation due to the aromatic difference between benzene and thiophene rings.When m-PhEh-BDD used as the third unit to modify the PM6,two new random polymers,namely FBDT-m10 and FBDT-m20 were obtained successfully.For direct comparison,the m-PhEh-BDD-based alternating polymer FBDT-m100 was also synthesized.With the mole content of m-PhEh-BDD moiety increasing,the highest occupied molecular orbital(HOMO)levels of the polymers gradually downshift but their bandgap values almost are identical.Moreover,FBDT-m100 shows less aggregation ability than PM6,suggesting that m-PhEh-BDD unit can modulate the aggregation behavior.Owing to the suitable aggregation and processibility,FBDT-m10 with moderate content of m-PhEh-BDD exhibits the best compatibility with non-fullerene acceptor Y6-BO,re-sulting in the superior blend morphology.Therefore,the as-cast devices based on FBDT-m10 can obtain the champion PCE of 16.06％,with a good fill factor of 71.14％.Additionally,the FBDT-m 10-based device shows better storage stability than that based on PM6.After 7 d of storage,FBDT-m 10-based device can maintain 87％of its initial PCE whereas the PM6-based device only kept 58％of its initial PCE.When the m-PhEh-BDD content increasing,the as-cast devices of the same storage time encounter a decrease in PCE,indicating suitable m-PhEh-BDD content is beneficial for long-term stability.This work demonstrates that the further exploitation on phenyl-substituted benzodithiophenedione unit could be a potential venue to achieve promising polymers for high-performing and stable organic solar cells.
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