摘要
Sorting out organic molecules with high thermopower is essential for understanding molecular thermoelectrics.The intermolecular coupling offers a unique chance to enhance the thermopower by tuning the bandgap structure of molecular devices,but the investigation of intermolecular coupling in bulk materials remains challenging.Herein,we investigated the thermopower of diketopyrrolopyrrole(DPP)cored single-molecule junctions with different coupling strengths by varying the packing density of the self-assembled monolayers(SAM)using a customized scanning tunneling microscope break junction(STM-BJ)technique.We found that the thermopower of DPP molecules could be enhanced up to one order of magnitude with increasing packing density,suggesting that the thermopower increases with larger neighboring intermolecular interactions.The combined density functional theory(DFT)calculations revealed that the closely-packed configuration brings stronger intermolecular coupling and then reduces the highest occupied molecular orbital(HOMO)-lowest unoccupied molecular orbital(LUMO)gap,leading to an enhanced thermopower.Our findings offer a new strategy for developing organic thermoelectric devices with high thermopower.
基金
supported by the National Natural Science Foundation of China(21722305,21933012,31871877)
the National Key R&D Program of China(2017YFA0204902)
Natural Science Foundation of Fujian Province(2018J06004)
Beijing National Laboratory for Molecular Sciences(BNLMS202010 and BNLMS202005)
the Fundamental Research Funds for the Central Universities(20720220020,20720220072,20720200068,20720190002)
supported by the Engineering and Physical Sciences Research Council(EPSRC,EP/M014452/1,EP/P027156/1,and EP/N03337X/1)
the European Commission,the Future and Emerging Technologies(FET)Open project 767187-QuIET and the European(EU)project Bac-to-Fuel.