Nonfused ring electron acceptors(NFREAs)have attracted much attention due to their concise synthetic routes and low cost.However,developing high-performance NFREAs with simple structure remains a great challenge.In th...Nonfused ring electron acceptors(NFREAs)have attracted much attention due to their concise synthetic routes and low cost.However,developing high-performance NFREAs with simple structure remains a great challenge.In this work,a simple building block(POBT)with noncovalently conformational locks(No CLs)was designed and synthesized.Single-crystal X-ray study indicated the presence of S…O NOCLs in POBT,thus enabling it to possess a coplanar conformation comparable to that of fused-ring CPT.Two novel NFREAs based on CPT and POBT were developed,namely TT-CPT and TT-POBT,respectively.Besides,TT-POBT possessed a smaller Stokes shift and a reduced reorganization energy compared with TT-CPT,indicating the introduction of S…O No CLs can enhance the molecular rigidity even if simplifying the molecular structure.As a result,the TT-POBT-based PSC device afforded an impressive power conversion efficiency of 11.15%,much higher than that of TT-CPT counterpart(7.03%),mainly resulting from the tighterπ-πstacking,improved and balanced charge transport,and more favorable film morphology.This work demonstrates the potential of the simple building block POBT with No CLs towards constructing low-cost and highperformance NFREAs.展开更多
We report that the twisted few layer graphite(tFL-graphite)is a new family of moiréheterostructures(MHSs),which has richer and highly tunable moiréflat band structures entirely distinct from all the known MH...We report that the twisted few layer graphite(tFL-graphite)is a new family of moiréheterostructures(MHSs),which has richer and highly tunable moiréflat band structures entirely distinct from all the known MHSs.A tFL-graphite is composed of two few-layer graphite(Bernal stacked multilayer graphene),which are stacked on each other with a small twisted angle.The moiréband structure of the tFL-graphite strongly depends on the layer number of its composed two van der Waals layers.Near the magic angle,a tFL-graphite always has two nearly flat bands coexisting with a few pairs of narrowed dispersive(parabolic or linear)bands at the Fermi level,thus,enhances the DOS at EF.This coexistence property may also enhance the possible superconductivity as been demonstrated in other multiband superconductivity systems.Therefore,we expect strong multiband correlation effects in tFL-graphite.Meanwhile,a proper perpendicular electric field can induce several isolated nearly flat bands with nonzero valley Chern number in some simple tFL-graphites,indicating that tFL-graphite is also a novel topological flat band system.展开更多
We study the electronic structure of double-twisted few-layer graphite(DTFLG),which consists of three few-layer graphites(FLGs),i.e.,an ABA-stacked graphene multilayer,stacked with two twist angles.We consider two cat...We study the electronic structure of double-twisted few-layer graphite(DTFLG),which consists of three few-layer graphites(FLGs),i.e.,an ABA-stacked graphene multilayer,stacked with two twist angles.We consider two categories of DTFLG,the alternately and chirally twisted cases,according to the rotation direction of the two twist angles.We show that,once the middle FLG of DTFLG is not thinner than the trilayer,both types of DTFLG can remarkably host two pairs of degenerate Moire flat bands(MFBs) at EF,twice that of the magic angle twisted bilayer graphene(TBG).The doubled MFBs of DTFLG lead to a doubled density of states(DOS) at the Fermi level EF,which implies much stronger correlation effects than TBG.The degeneracy of MFBs can be lifted by a perpendicular electric field,and the isolated MFBs have a nonzero valley Chern number.We also reveal the peculiar wave function patterns of the MFB s in DTFLG.Our results establish a new family of Moire systems that have a much higher DOS at EFand thus possibly much stronger correlation effects.展开更多
We discover a new wave localization mechanism in a periodic wave system,which can produce a novel type of flat band and is distinct from the known localization mechanisms,i.e.,Anderson localization and flat band latti...We discover a new wave localization mechanism in a periodic wave system,which can produce a novel type of flat band and is distinct from the known localization mechanisms,i.e.,Anderson localization and flat band lattices.The first example we give is a designed electron waveguide(EWG)on 2DEG with special periodic confinement potential.Numerical calculations show that,with proper confinement geometry,electrons can be completely localized in an open waveguide.We interpret this flat band localization(FBL)phenomenon by introducing the concept of self-localized orbitals.Essentially,each unit cell of the waveguide is equivalent to an artificial atom,where the self-localized orbital is a special eigenstate with unique spatial distribution.These self-localized orbitals form the flat bands in the waveguide.Such self-localized orbital induced FBL is a general phenomenon of wave motion,which can arise in any wave systems with carefully engineered boundary conditions.We then design a metallic waveguide(MWG)array to illustrate that similar FBL can be readily realized and observed with electromagnetic waves.展开更多
基金the National Natural Science Foundation of China(Nos.52103352,51925306 and 52120105006)National Key R&D Program of China(No.2018FYA 0305800)+3 种基金Key Research Program of Chinese Academy of Sciences(No.XDPB08-2)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB28000000)the Youth Innovation Promotion Association of Chinese Academy of Sciences(No.2022165)the Fundamental Research Funds for the Central Universities.
文摘Nonfused ring electron acceptors(NFREAs)have attracted much attention due to their concise synthetic routes and low cost.However,developing high-performance NFREAs with simple structure remains a great challenge.In this work,a simple building block(POBT)with noncovalently conformational locks(No CLs)was designed and synthesized.Single-crystal X-ray study indicated the presence of S…O NOCLs in POBT,thus enabling it to possess a coplanar conformation comparable to that of fused-ring CPT.Two novel NFREAs based on CPT and POBT were developed,namely TT-CPT and TT-POBT,respectively.Besides,TT-POBT possessed a smaller Stokes shift and a reduced reorganization energy compared with TT-CPT,indicating the introduction of S…O No CLs can enhance the molecular rigidity even if simplifying the molecular structure.As a result,the TT-POBT-based PSC device afforded an impressive power conversion efficiency of 11.15%,much higher than that of TT-CPT counterpart(7.03%),mainly resulting from the tighterπ-πstacking,improved and balanced charge transport,and more favorable film morphology.This work demonstrates the potential of the simple building block POBT with No CLs towards constructing low-cost and highperformance NFREAs.
基金the National Natural Science Foundation of China(Grant Nos.11874160,12141401,and 11534001)the National Key Research and Development Program of China(Grant No.2017YFA0403501)the Fundamental Research Funds for the Central Universities(HUST:2017KFYXJJ027).
文摘We report that the twisted few layer graphite(tFL-graphite)is a new family of moiréheterostructures(MHSs),which has richer and highly tunable moiréflat band structures entirely distinct from all the known MHSs.A tFL-graphite is composed of two few-layer graphite(Bernal stacked multilayer graphene),which are stacked on each other with a small twisted angle.The moiréband structure of the tFL-graphite strongly depends on the layer number of its composed two van der Waals layers.Near the magic angle,a tFL-graphite always has two nearly flat bands coexisting with a few pairs of narrowed dispersive(parabolic or linear)bands at the Fermi level,thus,enhances the DOS at EF.This coexistence property may also enhance the possible superconductivity as been demonstrated in other multiband superconductivity systems.Therefore,we expect strong multiband correlation effects in tFL-graphite.Meanwhile,a proper perpendicular electric field can induce several isolated nearly flat bands with nonzero valley Chern number in some simple tFL-graphites,indicating that tFL-graphite is also a novel topological flat band system.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11874160, 12141401, and 11534001)the National Key Research and Development Program of China (Grant No. 2017YFA0403501)+2 种基金the Fundamental Research Funds for the Central Universities (Grant No. HUST:2017KFYXJJ027)supported by the National Basic Research Program of China (Grant No.2015CB921102)the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB28000000)。
文摘We study the electronic structure of double-twisted few-layer graphite(DTFLG),which consists of three few-layer graphites(FLGs),i.e.,an ABA-stacked graphene multilayer,stacked with two twist angles.We consider two categories of DTFLG,the alternately and chirally twisted cases,according to the rotation direction of the two twist angles.We show that,once the middle FLG of DTFLG is not thinner than the trilayer,both types of DTFLG can remarkably host two pairs of degenerate Moire flat bands(MFBs) at EF,twice that of the magic angle twisted bilayer graphene(TBG).The doubled MFBs of DTFLG lead to a doubled density of states(DOS) at the Fermi level EF,which implies much stronger correlation effects than TBG.The degeneracy of MFBs can be lifted by a perpendicular electric field,and the isolated MFBs have a nonzero valley Chern number.We also reveal the peculiar wave function patterns of the MFB s in DTFLG.Our results establish a new family of Moire systems that have a much higher DOS at EFand thus possibly much stronger correlation effects.
基金supported by the National Natural Science Foundation of China (Grant Nos.11874160,12141401,and 11534001)the National Key Research and Development Program of China (No.2017YFA0403501)the Fundamental Research Funds for the Central Universities (HUST:2017KFYXJJ027).
文摘We discover a new wave localization mechanism in a periodic wave system,which can produce a novel type of flat band and is distinct from the known localization mechanisms,i.e.,Anderson localization and flat band lattices.The first example we give is a designed electron waveguide(EWG)on 2DEG with special periodic confinement potential.Numerical calculations show that,with proper confinement geometry,electrons can be completely localized in an open waveguide.We interpret this flat band localization(FBL)phenomenon by introducing the concept of self-localized orbitals.Essentially,each unit cell of the waveguide is equivalent to an artificial atom,where the self-localized orbital is a special eigenstate with unique spatial distribution.These self-localized orbitals form the flat bands in the waveguide.Such self-localized orbital induced FBL is a general phenomenon of wave motion,which can arise in any wave systems with carefully engineered boundary conditions.We then design a metallic waveguide(MWG)array to illustrate that similar FBL can be readily realized and observed with electromagnetic waves.
基金the National Natural Science Foundation of China(11534001,11874160,11274129,11874026,and 61405067)the National Key Research and Development Program of China(2017YFA0403501)+1 种基金the Fundamental Research Funds for the Central Universities(HUST:2017KFYXJJ027)the National Basic Research Program of China(2015CB921102).
基金Project supported by the Key Project of Colleges and Universities in Fujian Province Serving the Construction of the West-strait(No.A101)the Foundation for the 2013 Research Plan of University Key Teacher Domestic Visitor of the Ministry of Educationthe Foundation for the Second Batch of Key Teacher of Quanzhou Normal College(the personnel department of QNC[2012]No.1),China