The photovoltaic performance of perovskite solar cells(PSCs)can be improved by utilizing efficient front contact.However,it has always been a significant challenge for fabricating high-quality,scalable,controllable,an...The photovoltaic performance of perovskite solar cells(PSCs)can be improved by utilizing efficient front contact.However,it has always been a significant challenge for fabricating high-quality,scalable,controllable,and cost-effective front contact.This study proposes a realistic multi-layer front contact design to realize efficient single-junction PSCs and perovskite/perovskite tandem solar cells(TSCs).As a critical part of the front contact,we prepared a highly compact titanium oxide(TiO2)film by industrially viable Spray Pyrolysis Deposition(SPD),which acts as a potential electron transport layer(ETL)for the fabrication of PSCs.Optimization and reproducibility of the TiO2 ETL were discreetly investigated while fabricating a set of planar PSCs.As the front contact has a significant influence on the optoelectronic properties of PSCs,hence,we investigated the optics and electrical effects of PSCs by three-dimensional(3D)finite-difference time-domain(FDTD)and finite element method(FEM)rigorous simulations.The investigation allows us to compare experimental results with the outcome from simulations.Furthermore,an optimized single-junction PSC is designed to enhance the energy conversion efficiency(ECE)by>30% compared to the planar reference PSC.Finally,the study has been progressed to the realization of all-perovskite TSC that can reach the ECE,exceeding 30%.Detailed guidance for the completion of high-performance PSCs is provided.展开更多
Energy conversion efficiency losses and limits of perovskite/silicon tandem solar cells are investigated by detailed balance calculations and photon management.An extended Shockley-Queisser model is used to identify f...Energy conversion efficiency losses and limits of perovskite/silicon tandem solar cells are investigated by detailed balance calculations and photon management.An extended Shockley-Queisser model is used to identify fundamental loss mechanisms and link the losses to the optics of solar cells.Photon management is used to minimize losses and maximize the energy conversion efficiency.The influence of photon management on the solar cell parameters of a perovskite single-junction solar cell and a perovskite/silicon solar cell is discussed in greater details.An optimized solar cell design of a perovskite/silicon tandem solar cell is presented,which allows for the realization of solar cells with energy conversion efficiencies exceeding 32%.展开更多
Time reversal symmetry(TRS)is a key symmetry for classification of unconventional superconductors,and the violation of TRS often results in a wealth of novel properties.Here we report the synthesis and superconducting...Time reversal symmetry(TRS)is a key symmetry for classification of unconventional superconductors,and the violation of TRS often results in a wealth of novel properties.Here we report the synthesis and superconducting properties of the partially filled skutterudite Pr1-δPt4Ge12.The results from x-ray diffraction and magnetization measurements show that the[Pt4 Ge12]cage-forming structure survives and bulk superconductivity is preserved below the superconducting transition temperature Tc = 7.80 K.The temperature dependence of both the upper critical field and the electronic specific heat can be described in terms of a two-gap model,providing strong evidence of multi-band superconductivity.TRS breaking is observed using zero Held muon-spin relaxation experiments,and the magnitude of the spontaneous field is nearly half of that in PrPt4Ge12.展开更多
Recently, the quasi-two-dimensional electron gas (q2DEG) confined at the interface between LaAlO3 and SrTiO3 has attracted significant attention. In this paper, we briefly review experimental methods that have been ...Recently, the quasi-two-dimensional electron gas (q2DEG) confined at the interface between LaAlO3 and SrTiO3 has attracted significant attention. In this paper, we briefly review experimental methods that have been used to tune the carrier density and mobility of this q2DEG. These methods can be classified into two categories: growth-related tuning (i.e. substrate, growth temperature, oxygen pressure, post-annealing, LaAlO3 thickness, stoichiometry, and capping layers) and post-growth tuning (i.e. electrostatic field gating, conductive atomic force microscopy and surface adsorbates). Taken together, these methods enable the broad tuning of the electronic properties of this interface.展开更多
Shared-aperture technology for multifunctional planar systems,performing several simultaneous tasks,was first introduced in the field of radar antennas.In photonics,effective control of the electromagnetic response ca...Shared-aperture technology for multifunctional planar systems,performing several simultaneous tasks,was first introduced in the field of radar antennas.In photonics,effective control of the electromagnetic response can be achieved by a geometric-phase mechanism implemented within a metasurface,enabling spin-controlled phase modulation.The synthesis of the shared-aperture and geometric-phase concepts facilitates the generation of multifunctional metasurfaces.Here shared-aperture geometric-phase metasurfaces were realized via the interleaving of sparse antenna sub-arrays,forming Si-based devices consisting of multiplexed geometric-phase profiles.We study the performance limitations of interleaved nanoantenna arrays by means of a Wigner phasespace distribution to establish the ultimate information capacity of a metasurface-based photonic system.Within these limitations,we present multifunctional spin-dependent dielectric metasurfaces,and demonstrate multiple-beam technology for optical rotation sensing.We also demonstrate the possibility of achieving complete real-time control and measurement of the fundamental,intrinsic properties of light,including frequency,polarization and orbital angular momentum.展开更多
Three-dimensional (3D) topological insulators represent a new state of quantum matter with a bulk gap and odd number of relativistic Dirac fermions on the surface. The unusual surface states of topological insulator...Three-dimensional (3D) topological insulators represent a new state of quantum matter with a bulk gap and odd number of relativistic Dirac fermions on the surface. The unusual surface states of topological insulators rise from the nontrivial topology of their electronic structures as a result of strong spin-orbital coupling. In this review, we will briefly introduce the concept of topological insu- lators and the experimental method that can directly probe their unique electronic structure: angle resolved photoemission spectroscopy (ARPES). A few examples are then presented to demonstrate the unique band structures of different families of topological insulators and the unusual properties of the topological surface states. Finally, we will briefly discuss the future development of topological quantum materials.展开更多
基金supported in part by the Research and Study Project of Tokai University General Research Organization and by the Grant-in-Aid for Scientific Research Grant Number 20H02838the Universiti Kebangsaan Malaysia for supporting this study through FRGS/1/2017/TK07/UKM/02/9 Grantsupported by the Research Grants Council of Hong Kong,China(Project Number:152093/18E).
文摘The photovoltaic performance of perovskite solar cells(PSCs)can be improved by utilizing efficient front contact.However,it has always been a significant challenge for fabricating high-quality,scalable,controllable,and cost-effective front contact.This study proposes a realistic multi-layer front contact design to realize efficient single-junction PSCs and perovskite/perovskite tandem solar cells(TSCs).As a critical part of the front contact,we prepared a highly compact titanium oxide(TiO2)film by industrially viable Spray Pyrolysis Deposition(SPD),which acts as a potential electron transport layer(ETL)for the fabrication of PSCs.Optimization and reproducibility of the TiO2 ETL were discreetly investigated while fabricating a set of planar PSCs.As the front contact has a significant influence on the optoelectronic properties of PSCs,hence,we investigated the optics and electrical effects of PSCs by three-dimensional(3D)finite-difference time-domain(FDTD)and finite element method(FEM)rigorous simulations.The investigation allows us to compare experimental results with the outcome from simulations.Furthermore,an optimized single-junction PSC is designed to enhance the energy conversion efficiency(ECE)by>30% compared to the planar reference PSC.Finally,the study has been progressed to the realization of all-perovskite TSC that can reach the ECE,exceeding 30%.Detailed guidance for the completion of high-performance PSCs is provided.
基金financially supported by the Research Grants Council of Hong Kong,China(152093/18E)and the Hong Kong Polytechnic University(G-YBVG).
文摘Energy conversion efficiency losses and limits of perovskite/silicon tandem solar cells are investigated by detailed balance calculations and photon management.An extended Shockley-Queisser model is used to identify fundamental loss mechanisms and link the losses to the optics of solar cells.Photon management is used to minimize losses and maximize the energy conversion efficiency.The influence of photon management on the solar cell parameters of a perovskite single-junction solar cell and a perovskite/silicon solar cell is discussed in greater details.An optimized solar cell design of a perovskite/silicon tandem solar cell is presented,which allows for the realization of solar cells with energy conversion efficiencies exceeding 32%.
基金Supported by the National Key Research and Development Program of China under Grant Nos 2017YFA0303104 and2016YFA0300503the National Natural Science Foundation of China under Grant No 11774061the Chinese Government Scholarship of China Scholarship Council
文摘Time reversal symmetry(TRS)is a key symmetry for classification of unconventional superconductors,and the violation of TRS often results in a wealth of novel properties.Here we report the synthesis and superconducting properties of the partially filled skutterudite Pr1-δPt4Ge12.The results from x-ray diffraction and magnetization measurements show that the[Pt4 Ge12]cage-forming structure survives and bulk superconductivity is preserved below the superconducting transition temperature Tc = 7.80 K.The temperature dependence of both the upper critical field and the electronic specific heat can be described in terms of a two-gap model,providing strong evidence of multi-band superconductivity.TRS breaking is observed using zero Held muon-spin relaxation experiments,and the magnitude of the spontaneous field is nearly half of that in PrPt4Ge12.
基金Project supported by the Department of Energy,Office of Basic Energy Sciences(Grant No.DE-AC02-76SF00515)
文摘Recently, the quasi-two-dimensional electron gas (q2DEG) confined at the interface between LaAlO3 and SrTiO3 has attracted significant attention. In this paper, we briefly review experimental methods that have been used to tune the carrier density and mobility of this q2DEG. These methods can be classified into two categories: growth-related tuning (i.e. substrate, growth temperature, oxygen pressure, post-annealing, LaAlO3 thickness, stoichiometry, and capping layers) and post-growth tuning (i.e. electrostatic field gating, conductive atomic force microscopy and surface adsorbates). Taken together, these methods enable the broad tuning of the electronic properties of this interface.
基金supported by the Israel Science Foundation(ISF)the United States—Israel Binational Science Foundation(BSF)the Israel Ministry of Science,Technology and Space,and KLA-Tencor.
文摘Shared-aperture technology for multifunctional planar systems,performing several simultaneous tasks,was first introduced in the field of radar antennas.In photonics,effective control of the electromagnetic response can be achieved by a geometric-phase mechanism implemented within a metasurface,enabling spin-controlled phase modulation.The synthesis of the shared-aperture and geometric-phase concepts facilitates the generation of multifunctional metasurfaces.Here shared-aperture geometric-phase metasurfaces were realized via the interleaving of sparse antenna sub-arrays,forming Si-based devices consisting of multiplexed geometric-phase profiles.We study the performance limitations of interleaved nanoantenna arrays by means of a Wigner phasespace distribution to establish the ultimate information capacity of a metasurface-based photonic system.Within these limitations,we present multifunctional spin-dependent dielectric metasurfaces,and demonstrate multiple-beam technology for optical rotation sensing.We also demonstrate the possibility of achieving complete real-time control and measurement of the fundamental,intrinsic properties of light,including frequency,polarization and orbital angular momentum.
文摘Three-dimensional (3D) topological insulators represent a new state of quantum matter with a bulk gap and odd number of relativistic Dirac fermions on the surface. The unusual surface states of topological insulators rise from the nontrivial topology of their electronic structures as a result of strong spin-orbital coupling. In this review, we will briefly introduce the concept of topological insu- lators and the experimental method that can directly probe their unique electronic structure: angle resolved photoemission spectroscopy (ARPES). A few examples are then presented to demonstrate the unique band structures of different families of topological insulators and the unusual properties of the topological surface states. Finally, we will briefly discuss the future development of topological quantum materials.