Defect density is one of the most significant characteristics of perovskite single crystals(PSCs)that determines their optical and electrical properties,but few strategies are available to tune this property.Here,we d...Defect density is one of the most significant characteristics of perovskite single crystals(PSCs)that determines their optical and electrical properties,but few strategies are available to tune this property.Here,we demonstrate that voltage regulation is an efficient method to tune defect density,as well as the optical and electrical properties of PSCs.A three-step carrier transport model of MAPbBr_(3) PSCs is proposed to explore the defect regulation mechanism and carrier transport dynamics via an applied bias.Dynamic and steady-state photoluminescence measurements subsequently show that the surface defect density,average carrier lifetime,and photoluminescence intensity can be efficiently tuned by the applied bias.In particular,when the regulation voltage is 20 V(electrical poling intensity is 0.167 Vμm^(−1)),the surface defect density of MAPbBr_(3) PSCs is reduced by 24.27%,the carrier lifetime is prolonged by 32.04%,and the PL intensity is increased by 112.96%.Furthermore,a voltage-regulated MAPbBr_(3) PSC memristor device shows an adjustable multiresistance,weak ion migration effect and greatly enhanced device stability.Voltage regulation is a promising engineering technique for developing advanced perovskite optoelectronic devices.展开更多
The von Neumann bottleneck has spawned the rapid expansion of neuromorphic engineering and brain-like networks.Synapses serve as bridges for information transmission and connection in the biological nervous system.The...The von Neumann bottleneck has spawned the rapid expansion of neuromorphic engineering and brain-like networks.Synapses serve as bridges for information transmission and connection in the biological nervous system.The direct implementation of neural networks may depend on novel materials and devices that mimic natural neuronal and synaptic behavior.By exploiting the interfacial effects between MoS_(2) and AlOx,we demonstrate that an h-BN-encapsulated MoS_(2) artificial synapse transistor can mimic the basic synaptic behaviors,including EPSC,PPF,LTP,and LTD.Efficient optoelectronic spikes enable simulation of synaptic gain,frequency,and weight plasticity.The Pavlov classical conditioning experiment was successfully simulated by electrical tuning,showing associated learning behavior.In addition,h-BN encapsulation effectively improves the environmental time stability of our devices.Our h-BN-encapsulated MoS_(2) artificial synapse provides a new paradigm for hardware implementation of neuromorphic engineering.展开更多
In-plane birefringent materials present an effective modulation of the optical properties and more degrees of freedom for the signal detection in low dimension,and thus remain a hot topic in realizing the integrated,m...In-plane birefringent materials present an effective modulation of the optical properties and more degrees of freedom for the signal detection in low dimension,and thus remain a hot topic in realizing the integrated,miniature,and flexible devices for multiple applications.Here,the artificial in-plane birefringence properties have been successfully achieved on a graphene oxide film by a novel femtosecond laser lithography method,which provides a high-speed,large-area,and regular subwavelength gratings(~380 nm)fabrication and photoreduction.The obtained sample manifests an evident optical birefringence(~0.18)and anisotropic photoresponse(~1.21)in the visible range,both of which can be significantly modulated by either the structural morphology or the degree of oxide reduction.Based on the analysis of effective-medium theory and measurements of angle-resolved polarized Raman spectroscopy,the artificial in-plane birefringence is originated from various optical responses of the periodic subwavelength structures for the incident light with different polarization states.This technique shows great advantages for the fabrication of integrated in-plane polarization-dependent devices,which is expected to solve the problems in this field,such as the deficient selection of materials,complex design of micro/nanostructure,and inflexible processing technology.展开更多
基金supported by the National Key Research and Development Program of China(2018YFB1107202,2017YFB1104700)the Natural Science Foundation of China(NSFC,91750205,61774155,51102107)the K.C.Wong Education Foundation(GJTD-2018-08).
文摘Defect density is one of the most significant characteristics of perovskite single crystals(PSCs)that determines their optical and electrical properties,but few strategies are available to tune this property.Here,we demonstrate that voltage regulation is an efficient method to tune defect density,as well as the optical and electrical properties of PSCs.A three-step carrier transport model of MAPbBr_(3) PSCs is proposed to explore the defect regulation mechanism and carrier transport dynamics via an applied bias.Dynamic and steady-state photoluminescence measurements subsequently show that the surface defect density,average carrier lifetime,and photoluminescence intensity can be efficiently tuned by the applied bias.In particular,when the regulation voltage is 20 V(electrical poling intensity is 0.167 Vμm^(−1)),the surface defect density of MAPbBr_(3) PSCs is reduced by 24.27%,the carrier lifetime is prolonged by 32.04%,and the PL intensity is increased by 112.96%.Furthermore,a voltage-regulated MAPbBr_(3) PSC memristor device shows an adjustable multiresistance,weak ion migration effect and greatly enhanced device stability.Voltage regulation is a promising engineering technique for developing advanced perovskite optoelectronic devices.
基金This work was supported by the National Natural Science Foundation of China(61622401,61851402,and 61734003)the National Key Research and Development Program(2017YFB0405600)+1 种基金the Shanghai Education Development Foundation,and the Shanghai Municipal Education Commission Shuguang Program(18SG01)P.Z.also acknowledges support from the Shanghai Municipal Science and Technology Commission(grant no.18JC1410300)。
文摘The von Neumann bottleneck has spawned the rapid expansion of neuromorphic engineering and brain-like networks.Synapses serve as bridges for information transmission and connection in the biological nervous system.The direct implementation of neural networks may depend on novel materials and devices that mimic natural neuronal and synaptic behavior.By exploiting the interfacial effects between MoS_(2) and AlOx,we demonstrate that an h-BN-encapsulated MoS_(2) artificial synapse transistor can mimic the basic synaptic behaviors,including EPSC,PPF,LTP,and LTD.Efficient optoelectronic spikes enable simulation of synaptic gain,frequency,and weight plasticity.The Pavlov classical conditioning experiment was successfully simulated by electrical tuning,showing associated learning behavior.In addition,h-BN encapsulation effectively improves the environmental time stability of our devices.Our h-BN-encapsulated MoS_(2) artificial synapse provides a new paradigm for hardware implementation of neuromorphic engineering.
基金The research is financially supported by the K.C.Wong Education Foundation(No.GJTD-2018-08)the National Natural Science Foundation of China(Nos.91750205,11674178,and 11804334)the Jilin Provincial Science&Technology Development Project(No.20180414019GH)。
文摘In-plane birefringent materials present an effective modulation of the optical properties and more degrees of freedom for the signal detection in low dimension,and thus remain a hot topic in realizing the integrated,miniature,and flexible devices for multiple applications.Here,the artificial in-plane birefringence properties have been successfully achieved on a graphene oxide film by a novel femtosecond laser lithography method,which provides a high-speed,large-area,and regular subwavelength gratings(~380 nm)fabrication and photoreduction.The obtained sample manifests an evident optical birefringence(~0.18)and anisotropic photoresponse(~1.21)in the visible range,both of which can be significantly modulated by either the structural morphology or the degree of oxide reduction.Based on the analysis of effective-medium theory and measurements of angle-resolved polarized Raman spectroscopy,the artificial in-plane birefringence is originated from various optical responses of the periodic subwavelength structures for the incident light with different polarization states.This technique shows great advantages for the fabrication of integrated in-plane polarization-dependent devices,which is expected to solve the problems in this field,such as the deficient selection of materials,complex design of micro/nanostructure,and inflexible processing technology.
