Structural, electronic, and magnetic behaviors of 5d transition metal（TM） atom substituted divacancy（DV） graphene are investigated using first-principles calculations. Different 5d TM atoms（Hf, Ta, W, Re, Os, Ir,...Structural, electronic, and magnetic behaviors of 5d transition metal（TM） atom substituted divacancy（DV） graphene are investigated using first-principles calculations. Different 5d TM atoms（Hf, Ta, W, Re, Os, Ir, and Pt） are embedded in graphene, these impurity atoms replace 2 carbon atoms in the graphene sheet. It is revealed that the charge transfer occurs from 5d TM atoms to the graphene layer. Hf, Ta, and W substituted graphene structures exhibit a finite band gap at high symmetric K-point in their spin up and spin down channels with 0.783 μB, 1.65 μB, and 1.78 μB magnetic moments,respectively. Ir and Pt substituted graphene structures display indirect band gap semiconductor behavior. Interestingly, Os substituted graphene shows direct band gap semiconductor behavior having a band gap of approximately 0.4 e V in their spin up channel with 1.5 μB magnetic moment. Through density of states（DOS） analysis, we can predict that d orbitals of 5d TM atoms could be responsible for introducing ferromagnetism in the graphene layer. We believe that our obtained results provide a new route for potential applications of dilute magnetic semiconductors and half-metals in spintronic devices by employing 5d transition metal atom-doped graphene complexes.展开更多
Rapid halide anion exchange easily occurring in metal-halide perovskite nanoparticles(NPs)makes it nearly impossible to create a single three-dimensional(3D)CsPbX_(3)(X=Cl,Br,I)NP that simultaneously comprises two sep...Rapid halide anion exchange easily occurring in metal-halide perovskite nanoparticles(NPs)makes it nearly impossible to create a single three-dimensional(3D)CsPbX_(3)(X=Cl,Br,I)NP that simultaneously comprises two separate perovskite components.To circumvent this problem,we first propose a Ni^(2+)-mediated halide anion-exchange strategy in zero-dimensional(0D)Ni^(2+)-doped Cs_(4)PbBr_(6)(Cs_(4)PbBr_(6):Ni)perovskites to achieve ultra-stable 3D CsPbX_(3)NPs with two coexisting different perovskite individuals of CsPbCl_(3)and/or CsPbBr_(3).By combining the experimental results with first-principles calculations,we confirm that the completely isolated[PbBr_(6)]4−octahedra in 0D Cs_(4)PbBr_(6):Ni NPs can restrict rapid halide anion exchange and the anion diffusion preferentially proceeds in the proximity of substitutional NiPb centers,namely[NiBr_(6)]4−octahedra in a meta-stable state,rather than in the 0D Cs_(4)PbBr_(6)and residual 3D CsPbBr_(3)regions,thereby delivering intrinsic dual-band excitonic luminescence from a single 3D CsPbX_(3)NP with a more stable and efficient CsPbCl_(3)component as compared to its counterparts synthesized using conventional methods.These new insights regarding the precise control of halide anion exchange enable the preparation of a new type of high-efficiency perovskite materials with suppressed anion interdiffusion for prospective optoelectronic devices.展开更多
One challenge to the use of lightly-doped, high efficiency emitters on multicrystalline silicon wafers is the poor gettering efficiency of the diffusion processes used to fabricate them. With the photovoltaic industry...One challenge to the use of lightly-doped, high efficiency emitters on multicrystalline silicon wafers is the poor gettering efficiency of the diffusion processes used to fabricate them. With the photovoltaic industry highly reliant on heavily doped phosphorus diffusions as a source of gettering, the transition to selective emitter structures would require new alternative methods of impurity extraction. In this paper, a novel laser based method for gettering is investigated for available silicon wafers used its impact on commercially in the manufacturing of solar cells. Direct comparisons between laser enhanced gettering （LasEG） and lightly-doped emitter diffusion gettering demonstrate a 45% absolute improvement in bulk minority carrier lifetime when using the laser process. Although grain boundaries can be effective gettering sites in multicrystalline wafers, laser processing can substantially improve the performance of both grain boundary sites and intra-grain regions. This improvement is correlated with a factor of 6 further decrease in interstitial iron concentra- tions. The removal of such impurities from multicrystalline wafers using the laser process can result in intra-grain enhancements in implied open-circuit voltage of up to 40 mV. In instances where specific dopant profiles are required for a diffusion on one surface of a solar cell, and the diffusion process does not enable effective gettering, LasEG may enable improved gettering during the diffusion process.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51522601 and 51421063)the Program for New Century Excellent Talents in University,China(Grant No.NCET-13-0173)
文摘Structural, electronic, and magnetic behaviors of 5d transition metal（TM） atom substituted divacancy（DV） graphene are investigated using first-principles calculations. Different 5d TM atoms（Hf, Ta, W, Re, Os, Ir, and Pt） are embedded in graphene, these impurity atoms replace 2 carbon atoms in the graphene sheet. It is revealed that the charge transfer occurs from 5d TM atoms to the graphene layer. Hf, Ta, and W substituted graphene structures exhibit a finite band gap at high symmetric K-point in their spin up and spin down channels with 0.783 μB, 1.65 μB, and 1.78 μB magnetic moments,respectively. Ir and Pt substituted graphene structures display indirect band gap semiconductor behavior. Interestingly, Os substituted graphene shows direct band gap semiconductor behavior having a band gap of approximately 0.4 e V in their spin up channel with 1.5 μB magnetic moment. Through density of states（DOS） analysis, we can predict that d orbitals of 5d TM atoms could be responsible for introducing ferromagnetism in the graphene layer. We believe that our obtained results provide a new route for potential applications of dilute magnetic semiconductors and half-metals in spintronic devices by employing 5d transition metal atom-doped graphene complexes.
基金supported by the Fund of Fujian Science&Technology Innovation Laboratory for Optoelectronic Information(grant nos.2020ZZ114 and 2022ZZ204)the Key Research Program of Frontier Science CAS(grant no.QYZDY-SSW-SLH025)+1 种基金the National Natural Science Foundation of China(grant nos.21731006 and 21871256)the Fund of Advanced Energy Science and Technology Guangdong Laboratory(grant no.DJLTN0200/DJLTN0240).
文摘Rapid halide anion exchange easily occurring in metal-halide perovskite nanoparticles(NPs)makes it nearly impossible to create a single three-dimensional(3D)CsPbX_(3)(X=Cl,Br,I)NP that simultaneously comprises two separate perovskite components.To circumvent this problem,we first propose a Ni^(2+)-mediated halide anion-exchange strategy in zero-dimensional(0D)Ni^(2+)-doped Cs_(4)PbBr_(6)(Cs_(4)PbBr_(6):Ni)perovskites to achieve ultra-stable 3D CsPbX_(3)NPs with two coexisting different perovskite individuals of CsPbCl_(3)and/or CsPbBr_(3).By combining the experimental results with first-principles calculations,we confirm that the completely isolated[PbBr_(6)]4−octahedra in 0D Cs_(4)PbBr_(6):Ni NPs can restrict rapid halide anion exchange and the anion diffusion preferentially proceeds in the proximity of substitutional NiPb centers,namely[NiBr_(6)]4−octahedra in a meta-stable state,rather than in the 0D Cs_(4)PbBr_(6)and residual 3D CsPbBr_(3)regions,thereby delivering intrinsic dual-band excitonic luminescence from a single 3D CsPbX_(3)NP with a more stable and efficient CsPbCl_(3)component as compared to its counterparts synthesized using conventional methods.These new insights regarding the precise control of halide anion exchange enable the preparation of a new type of high-efficiency perovskite materials with suppressed anion interdiffusion for prospective optoelectronic devices.
文摘One challenge to the use of lightly-doped, high efficiency emitters on multicrystalline silicon wafers is the poor gettering efficiency of the diffusion processes used to fabricate them. With the photovoltaic industry highly reliant on heavily doped phosphorus diffusions as a source of gettering, the transition to selective emitter structures would require new alternative methods of impurity extraction. In this paper, a novel laser based method for gettering is investigated for available silicon wafers used its impact on commercially in the manufacturing of solar cells. Direct comparisons between laser enhanced gettering （LasEG） and lightly-doped emitter diffusion gettering demonstrate a 45% absolute improvement in bulk minority carrier lifetime when using the laser process. Although grain boundaries can be effective gettering sites in multicrystalline wafers, laser processing can substantially improve the performance of both grain boundary sites and intra-grain regions. This improvement is correlated with a factor of 6 further decrease in interstitial iron concentra- tions. The removal of such impurities from multicrystalline wafers using the laser process can result in intra-grain enhancements in implied open-circuit voltage of up to 40 mV. In instances where specific dopant profiles are required for a diffusion on one surface of a solar cell, and the diffusion process does not enable effective gettering, LasEG may enable improved gettering during the diffusion process.
