To gain further understanding of the luminescence properties of multiquantum wells and the factors affecting them on a microscopic level,cathodoluminescence combined with scanning transmission electron microscopy and ...To gain further understanding of the luminescence properties of multiquantum wells and the factors affecting them on a microscopic level,cathodoluminescence combined with scanning transmission electron microscopy and spectroscopy was used to measure the luminescence of In_(0.15)Ga_(0.85)N five-period multiquantum wells.The lattice-composition-energy relationship was established with the help of energy-dispersive x-ray spectroscopy,and the bandgaps of In_(0.15)Ga_(0.85)N and GaN in multiple quantum wells were extracted by electron energy loss spectroscopy to understand the features of cathodoluminescence spectra.The luminescence differences between different periods of multiquantum wells and the effects of defects such as composition fluctuation and dislocations on the luminescence of multiple quantum wells were revealed.Our study establishing the direct relationship between the atomic structure of In_(x)Ga_(1-x)N multiquantum wells and photoelectric properties provides useful information for nitride applications.展开更多
With recent developments of deep ultraviolet(DUV)light-emitting diodes and solar-blind detectors,UV communication(UVC)shows great potential in replacing traditional wireless communication in more and more scenarios.Ba...With recent developments of deep ultraviolet(DUV)light-emitting diodes and solar-blind detectors,UV communication(UVC)shows great potential in replacing traditional wireless communication in more and more scenarios.Based on the atmospheric scattering of UV radiation,UVC has gained considerable attention due to its non-line-of-sight ability,omnidirectional communication links and low background noise.These advantages make UVC an ideal option for covert secure communication,especially for military communication.In this review,we present the history and working principle of UVC with a special focus on its light sources and detectors.Comprehensive comparison and application of its light sources and detectors are provided to the best of our knowledge.We further discuss the future application and outlook of UVC.Hopefully,this review will offer valuable insights into the future development of UVC.展开更多
An efficient solution-processable route employing Pb(Ac)2 as lead source and anti-solvent treatment to achieve fully covered and homogenous perovskite films is reported. The effect of different solution methods and de...An efficient solution-processable route employing Pb(Ac)2 as lead source and anti-solvent treatment to achieve fully covered and homogenous perovskite films is reported. The effect of different solution methods and device architectures on the morphologies of perovskite films were systematically investigated. Our results show that the planar perovskite layer fabricated by one-step solution method achieved fully covered and pinhole-free films. Further anti-solvent treatment using chlorobenzene (CB) promoted a perovskite film with highly smooth surfaces and enlarged grain sizes. Device fabricated from CB treated perovskite film achieved a best PCE of 15.80%, in comparison with 14.02%for the untreated device. These results evidently suggest a feasible route towards controlling the crystallization and morphology of planar heterojunction (PHJ) PSCs for improved efficiency.展开更多
Phonons are the primary heat carriers in non-metallic solids.In compositionally heterogeneous materials,the thermal properties are believed to be mainly governed by the disrupted phonon transport due to mass disorder ...Phonons are the primary heat carriers in non-metallic solids.In compositionally heterogeneous materials,the thermal properties are believed to be mainly governed by the disrupted phonon transport due to mass disorder and strain fluctuations,while the effects of compositional fluctuation induced local phonon states are usually ignored.Here,by scanning transmission electron microscopy electron energy loss spectroscopy and sophisticated calculations,we identify the vibrational properties of ingredient-dependent interface phonon modes in Alx Ga1-x N and quantify their various contributions to the local interface thermal conductance.We demonstrate that atomic-scale compositional fluctuation has significant influence on the vibrational thermodynamic properties,highly affecting the mode ratio and vibrational amplitude of interface phonon modes and subsequently redistributing their modal contribution to the interface thermal conductance.Our work provides fundamental insights into understanding of local phonon-boundary interactions in nanoscale inhomogeneities,which reveal new opportunities for optimization of thermal properties via engineering ingredient distribution.展开更多
Three novel copolymers,poly[1-（4-（benzothiazole-2-thio-alkyloxy）-biphenyl-4＇-oxy）2.3-epoxypropane]s,were synthesized by the reaction of polyepichlorohydrin with obtained monomers,4-（benzothiazole-2-thio-alkyloxy...Three novel copolymers,poly[1-（4-（benzothiazole-2-thio-alkyloxy）-biphenyl-4＇-oxy）2.3-epoxypropane]s,were synthesized by the reaction of polyepichlorohydrin with obtained monomers,4-（benzothiazole-2-thio-alkyloxy）biphenyl-4＇-ols,in which the number of methylene unit in substitution group of biphenyl group was 2,4,6,respectively.The structures of obtained compounds were confirmed by elemental analysis and 1H NMR.The decomposition temperatures of copolymers were near 340 ℃.Differential scanning calorimetry（DSC） measurement and polarized optical microscopy（POM） observation showed the resulting copolymers did not exhibit thermotropic liquid crystalline mesomophism and belonged to semi-crystalline substance.展开更多
Due to their good color rendering ability, white light-emitting diodes(WLEDs) with conventional phosphor and quantum dots(QDs) are gaining increasing attention. However, their optical and thermal performances are stil...Due to their good color rendering ability, white light-emitting diodes(WLEDs) with conventional phosphor and quantum dots(QDs) are gaining increasing attention. However, their optical and thermal performances are still limited especially for the ones with QDs-phosphor mixed nanocomposites. In this work, we propose a novel packaging scheme with horizontally layered QDs-phosphor nanocomposites to obtain an enhanced optical and thermal performance for WLEDs. Three different WLEDs, including QDs-phosphor mixed type, QDsoutside type, and QDs-inside type, were fabricated and compared. With 30 wt. % phosphor and 0.15 wt. % QDs nanocomposite, the QDs-outside type WLED shows a 21.8% increase of luminous efficiency, better color rendering ability, and a 27.0% decrease of the maximum nanocomposite temperature at 400 mA, compared with the mixed-type WLED. The reduced re-absorption between phosphor and QDs is responsible for the performance enhancement when they are separated. However, such reduced absorption can be traded off by the improper layered configuration, which is demonstrated by the worst performance of the QDs-inside type. Further, we demonstrate that the higher energy transfer efficiency between excitation light and nanocomposite in the QDs-outside type WLED is the key reason for its enhanced optical and thermal performance.展开更多
The energy-efficient deep ultraviolet(DUV)optoelectronic devices suffer from critical issues associated with the poor quality and large strain of nitride material system caused by the inherent mismatch of heteroepitax...The energy-efficient deep ultraviolet(DUV)optoelectronic devices suffer from critical issues associated with the poor quality and large strain of nitride material system caused by the inherent mismatch of heteroepitaxy.In this work,we have prepared the strain-free AlN film with low dislocation density(DD)by graphene(Gr)-driving strain-pre-store engineering and a unique mechanism of strain-relaxation in quasi-van der Waals(QvdW)epitaxy is presented.The DD in AlN epilayer with Gr exhibits an anomalous sawtooth-like evolution during the whole epitaxy process.Gr can help to enable the annihilation of the dislocations originated from the interface between AlN and Gr/sapphire by impelling a lateral two-dimensional growth mode.Remarkably,it can induce AlN epilayer to pre-store sufficient tensile strain during the early growth stage and thus compensate the compressive strain caused by hetero-mismatch.Therefore,the low-strain state of the DUV light-emitting diode(DUV-LED)epitaxial structure is realized on the strain-free AlN template with Gr.Furthermore,the DUV-LED with Gr demonstrate 2.1 times enhancement of light output power and a better stability of luminous wavelength compared to that on bare sapphire.An in-depth understanding of this work reveals diverse beneficial impacts of Gr on nitride growth and provides a novel strategy of relaxing the vital requirements of hetero-mismatch in conventional heteroepitaxy.展开更多
Owing to their high color purity,tunable bandgap,and high efficiency,quantum dots(QDs)have gained significant attention as color conversion materials for high-end display applications.Moreover,inkjet-printed QD pixels...Owing to their high color purity,tunable bandgap,and high efficiency,quantum dots(QDs)have gained significant attention as color conversion materials for high-end display applications.Moreover,inkjet-printed QD pixels show great potential for realizing full-color mini/micro-light emitting diode(micro-LED)-based displays.As a color conversion layer,the photoluminescence intensity of QDs is limited by the insufficient absorptance of the excitation light due to the lack of scattering.Conventional scatterers,such as titanium dioxide microparticles,have been applied after additional surface engineering for sufficient dispersity to prevent nozzle clogging in inkjet printing process.In our work,as an alternative approach,we use inkjet printing for depositing a phase separating polymer ink based on polystyrene(PS)and polyethylene glycol(PEG).QD/polymer composite pixels with scattering micropores are realized.The morphology of the micropores can be tailored by the weight ratio between PS and PEG which enables the manipulation of scattering capability.With the presence of the microporous structure,the photoluminescence intensity of the QD film is enhanced by 110%in drop-cast films and by 35.3%in inkjet-printed QD pixel arrays compared to the reference samples.展开更多
The introduction of two-photon polymerization(TPP)into the area of Carbon Micro Electromechanical Systems(CMEMS)has enabled the fabrication of three-dimensional glassy carbon nanostructures with geometries previously ...The introduction of two-photon polymerization(TPP)into the area of Carbon Micro Electromechanical Systems(CMEMS)has enabled the fabrication of three-dimensional glassy carbon nanostructures with geometries previously unattainable through conventional UV lithography.Pyrolysis of TPP structures conveys a characteristic reduction of feature size—one that should be properly estimated in order to produce carbon microdevices with accuracy.In this work,we studied the volumetric shrinkage of TPP-derived microwires upon pyrolysis at 900℃.Through this process,photoresist microwires thermally decompose and shrink by as much as 75%,resulting in glassy carbon nanowires with linewidths between 300 and 550 nm.Even after the thermal decomposition induced by the pyrolysis step,the linewidth of the carbon nanowires was found to be dependent on the TPP exposure parameters.We have also found that the thermal stress induced during the pyrolysis step not only results in axial elongation of the nanowires,but also in buckling in the case of slender carbon nanowires(for aspect ratios greater than 30).Furthermore,we show that the calculated residual mass fraction that remains after pyrolysis depends on the characteristic dimensions of the photoresist microwires,a trend that is consistent with several works found in the literature.This phenomenon is explained through a semi-empirical model that estimates the feature size of the carbon structures,serving as a simple guideline for shrinkage evaluation in other designs.展开更多
Energy-harvesting from low-temperature environmental heat via thermoelectric generators(TEG)is a versatile and maintenancefree solution for large-scale waste heat recovery and supplying renewable energy to a growing n...Energy-harvesting from low-temperature environmental heat via thermoelectric generators(TEG)is a versatile and maintenancefree solution for large-scale waste heat recovery and supplying renewable energy to a growing number of devices in the Internet of Things(IoT)that require an independent wireless power supply.A prerequisite for market competitiveness,however,is the costeffective and scalable manufacturing of these TEGs.Our approach is to print the devices using printable thermoelectric polymers and composite materials.We present a mass-producible potentially low-cost fully screen printed flexible origami TEG.Through a unique two-step folding technique,we produce a mechanically stable 3D cuboidal device from a 2D layout printed on a thin flexible substrate using thermoelectric inks based on PEDOT nanowires and a TiS2:Hexylamine-complex material.We realize a device architecture with a high thermocouple density of 190 per cm2 by using the thin substrate as electrical insulation between the thermoelectric elements resulting in a high-power output of 47.8μWcm^(−2)from a 30 K temperature difference.The device properties are adjustable via the print layout,specifically,the thermal impedance of the TEGs can be tuned over several orders of magnitudes allowing thermal impedance matching to any given heat source.We demonstrate a wireless energy-harvesting application by powering an autonomous weather sensor comprising a Bluetooth module and a power management system.展开更多
Upcoming technologies in the fields of flexible electronics require the cost-efficient fabrication of complex circuitry in a streamlined process.Digital printing techniques such as inkjet printing can enable such appl...Upcoming technologies in the fields of flexible electronics require the cost-efficient fabrication of complex circuitry in a streamlined process.Digital printing techniques such as inkjet printing can enable such applications thanks to their inherent freedom of design permitting the mask-free deposition of multilayer optoelectronic devices without the need for subtracting techniques.Here we present an active matrix sensor array comprised of 100 inkjet-printed organic thin film transistors(OTFTs)and organic photodiodes(OPDs)monolithically integrated onto the same ultrathin substrate.Both the OTFTs and OPDs exhibited high-fabrication yield and state-of-the-art performance after the integration process.By scaling of the OPDs,we achieved integrated pixels with power consumptions down to 50 nW at one of the highest sensitivities reported to date for an all-organic integrated sensor.Finally,we demonstrated the application potential of the active matrix by static and dynamic spatial sensing of optical signals.展开更多
Ternary absorber blends have recently been identified as promising concepts to spectrally broaden the absorption of organic bulkheterojunction solar cells and hence to improve their power conversion efficiencies.In th...Ternary absorber blends have recently been identified as promising concepts to spectrally broaden the absorption of organic bulkheterojunction solar cells and hence to improve their power conversion efficiencies.In this work,we demonstrate that D-D-A ternary blends comprising two donor polymers and the acceptor PC61BM can also significantly enhance the thermal stability of the solar cell.Upon harsh thermal stress at 120°C for 2 h,the ternary solar cells show only a minor relative deterioration of 10%.Whereas the polymer/fullerene blend PTB7-Th:PC61BM is rather unstable under these conditions,its degradation was efficiently suppressed by incorporating the near infrared-absorbing polymer PDTP–DFBT.Spectroscopic ellipsometry investigations and an effective medium analysis of the ternary absorber blend revealed that the domain conformation in presence of PDTP–DFBT remains stable whereas the domain conformation changes in its absence.The ternary PTB7-Th:PDTP–DFBT:PC61BM solar cells yield thermally stable power conversion efficiencies of up to 6%.展开更多
X-ray detectors are of pivotal importance for the scientific and technological progress in a wide range of medical,industrial,and scientific applications.Here,we take advantage of the printability of perovskite-based ...X-ray detectors are of pivotal importance for the scientific and technological progress in a wide range of medical,industrial,and scientific applications.Here,we take advantage of the printability of perovskite-based semiconductors and achieve a high X-ray sensitivity combined with the potential of an exceptional high spatial resolution by our origami-inspired folded perovskite X-ray detector.The high performance of our device is reached solely by the folded detector architecture and does not require any photolithography.The design and fabrication of a foldable perovskite sensor array is presented and the detector is characterized as a planar and as a folded device.Exposed to 50 kVp−150 kVp X-ray radiation,the planar detector reaches X-ray sensitivities of 25−35μC/(Gyaircm^(2)),whereas the folded detector achieves remarkably increased X-ray sensitivities of several hundredμC/(Gyaircm^(2))and a record value of 1409μC/(Gyaircm^(2))at 150 kVp without photoconductive gain.Finally,the potential of an exceptional high spatial resolution of the folded detector of more than 20 lp/mm under 150 kVp X-ray radiation is demonstrated.展开更多
Heteroepitaxy can reduce the cost and widen the application range of semiconductor film synthesis and device fabrication.However,the lattice and thermal expansion coefficient mismatches between epilayers and substrate...Heteroepitaxy can reduce the cost and widen the application range of semiconductor film synthesis and device fabrication.However,the lattice and thermal expansion coefficient mismatches between epilayers and substrates limit the improvement of crystal quality and device performance.Two-dimensional(2D)material-assisted heteroepitaxy offers an effective solution to these challenges.The weak interaction at the interface between films and substrates facilitates the subsequent exfoliation and transfer of epilayer for the fabrication of flexible or high-power electronics.Herein,we summarize the modes of 2D material-assisted epitaxy,which can be classified into remote epitaxy,pinhole epitaxy and van der Waals epitaxy based on the interfacial interaction between the epilayers and substrates.Furthermore,we discuss in detail the improved crystal quality and functional applications,such as flexible devices,wavelength-modulated optoelectronic devices,and thermal management in high-power devices.Moreover,we highlight the challenges and prospects of 2D material-assisted epitaxy,providing roadmaps for lateral research and semiconductor production.展开更多
基金Project supported by the National Key R&D Program of China (Grant No. 2019YFA0708202)the National Natural Science Foundation of China (Grant Nos. 11974023, 52021006, 61974139, 12074369, and 12104017)+1 种基金the “2011 Program” from the Peking–Tsinghua–IOP Collaborative Innovation Center of Quantum Matterthe Youth Supporting Program of Institute of Semiconductors
文摘To gain further understanding of the luminescence properties of multiquantum wells and the factors affecting them on a microscopic level,cathodoluminescence combined with scanning transmission electron microscopy and spectroscopy was used to measure the luminescence of In_(0.15)Ga_(0.85)N five-period multiquantum wells.The lattice-composition-energy relationship was established with the help of energy-dispersive x-ray spectroscopy,and the bandgaps of In_(0.15)Ga_(0.85)N and GaN in multiple quantum wells were extracted by electron energy loss spectroscopy to understand the features of cathodoluminescence spectra.The luminescence differences between different periods of multiquantum wells and the effects of defects such as composition fluctuation and dislocations on the luminescence of multiple quantum wells were revealed.Our study establishing the direct relationship between the atomic structure of In_(x)Ga_(1-x)N multiquantum wells and photoelectric properties provides useful information for nitride applications.
基金financially supported by the National Key R&D Program of China(No.2019YFA0708203)the National Natural Science Foundation of China(No.61974139)the Beijing Natural Science Foundation(No.4182063)。
文摘With recent developments of deep ultraviolet(DUV)light-emitting diodes and solar-blind detectors,UV communication(UVC)shows great potential in replacing traditional wireless communication in more and more scenarios.Based on the atmospheric scattering of UV radiation,UVC has gained considerable attention due to its non-line-of-sight ability,omnidirectional communication links and low background noise.These advantages make UVC an ideal option for covert secure communication,especially for military communication.In this review,we present the history and working principle of UVC with a special focus on its light sources and detectors.Comprehensive comparison and application of its light sources and detectors are provided to the best of our knowledge.We further discuss the future application and outlook of UVC.Hopefully,this review will offer valuable insights into the future development of UVC.
基金supported by the National Natural Science Foundation of China(NSFC,Nos.51572072 and 21402045)Wuhan Science and Technology Bureau of Hubei Province of China (No. 2013010602010209)+1 种基金Educational Commission of Hubei Province of China(No. D20141006)Department of Science & Technology of Hubei Province of China(No. 2015CFA118)
文摘An efficient solution-processable route employing Pb(Ac)2 as lead source and anti-solvent treatment to achieve fully covered and homogenous perovskite films is reported. The effect of different solution methods and device architectures on the morphologies of perovskite films were systematically investigated. Our results show that the planar perovskite layer fabricated by one-step solution method achieved fully covered and pinhole-free films. Further anti-solvent treatment using chlorobenzene (CB) promoted a perovskite film with highly smooth surfaces and enlarged grain sizes. Device fabricated from CB treated perovskite film achieved a best PCE of 15.80%, in comparison with 14.02%for the untreated device. These results evidently suggest a feasible route towards controlling the crystallization and morphology of planar heterojunction (PHJ) PSCs for improved efficiency.
基金the National Key R&D Program of China(Grant No.2019YFA0708200)the National Natural Science Foundation of China(Grant Nos.52125307,11974023,12104017,and 52021006)+1 种基金the“2011 Program”from the Peking-Tsinghua-IOP Collaborative Innovation Center of Quantum MatterYouth Innovation Promotion Association,CAS。
文摘Phonons are the primary heat carriers in non-metallic solids.In compositionally heterogeneous materials,the thermal properties are believed to be mainly governed by the disrupted phonon transport due to mass disorder and strain fluctuations,while the effects of compositional fluctuation induced local phonon states are usually ignored.Here,by scanning transmission electron microscopy electron energy loss spectroscopy and sophisticated calculations,we identify the vibrational properties of ingredient-dependent interface phonon modes in Alx Ga1-x N and quantify their various contributions to the local interface thermal conductance.We demonstrate that atomic-scale compositional fluctuation has significant influence on the vibrational thermodynamic properties,highly affecting the mode ratio and vibrational amplitude of interface phonon modes and subsequently redistributing their modal contribution to the interface thermal conductance.Our work provides fundamental insights into understanding of local phonon-boundary interactions in nanoscale inhomogeneities,which reveal new opportunities for optimization of thermal properties via engineering ingredient distribution.
基金Funded by the National Natural Science Foundation of China (No.200474049)Specialized Research Fund for the Doctoral Program of Higher Education of China (No.20040497001)
文摘Three novel copolymers,poly[1-（4-（benzothiazole-2-thio-alkyloxy）-biphenyl-4＇-oxy）2.3-epoxypropane]s,were synthesized by the reaction of polyepichlorohydrin with obtained monomers,4-（benzothiazole-2-thio-alkyloxy）biphenyl-4＇-ols,in which the number of methylene unit in substitution group of biphenyl group was 2,4,6,respectively.The structures of obtained compounds were confirmed by elemental analysis and 1H NMR.The decomposition temperatures of copolymers were near 340 ℃.Differential scanning calorimetry（DSC） measurement and polarized optical microscopy（POM） observation showed the resulting copolymers did not exhibit thermotropic liquid crystalline mesomophism and belonged to semi-crystalline substance.
基金National Natural Science Foundation of China(NSFC)(51405161,U1401249)Natural Science Foundation of Guangdong Province(2014A030312017)+1 种基金Science & Technology Program of Guangdong Province(2015B010132002)China Scholarship Council(CSC)(201706150050)
文摘Due to their good color rendering ability, white light-emitting diodes(WLEDs) with conventional phosphor and quantum dots(QDs) are gaining increasing attention. However, their optical and thermal performances are still limited especially for the ones with QDs-phosphor mixed nanocomposites. In this work, we propose a novel packaging scheme with horizontally layered QDs-phosphor nanocomposites to obtain an enhanced optical and thermal performance for WLEDs. Three different WLEDs, including QDs-phosphor mixed type, QDsoutside type, and QDs-inside type, were fabricated and compared. With 30 wt. % phosphor and 0.15 wt. % QDs nanocomposite, the QDs-outside type WLED shows a 21.8% increase of luminous efficiency, better color rendering ability, and a 27.0% decrease of the maximum nanocomposite temperature at 400 mA, compared with the mixed-type WLED. The reduced re-absorption between phosphor and QDs is responsible for the performance enhancement when they are separated. However, such reduced absorption can be traded off by the improper layered configuration, which is demonstrated by the worst performance of the QDs-inside type. Further, we demonstrate that the higher energy transfer efficiency between excitation light and nanocomposite in the QDs-outside type WLED is the key reason for its enhanced optical and thermal performance.
基金financially supported by the National Key R&D Program of China(No.2019YFA0708203)the National Natural Science Foundation of China(Nos.61974139,52192614 and 12074369)Beijing Natural Science Foundation(No.4222077)。
文摘The energy-efficient deep ultraviolet(DUV)optoelectronic devices suffer from critical issues associated with the poor quality and large strain of nitride material system caused by the inherent mismatch of heteroepitaxy.In this work,we have prepared the strain-free AlN film with low dislocation density(DD)by graphene(Gr)-driving strain-pre-store engineering and a unique mechanism of strain-relaxation in quasi-van der Waals(QvdW)epitaxy is presented.The DD in AlN epilayer with Gr exhibits an anomalous sawtooth-like evolution during the whole epitaxy process.Gr can help to enable the annihilation of the dislocations originated from the interface between AlN and Gr/sapphire by impelling a lateral two-dimensional growth mode.Remarkably,it can induce AlN epilayer to pre-store sufficient tensile strain during the early growth stage and thus compensate the compressive strain caused by hetero-mismatch.Therefore,the low-strain state of the DUV light-emitting diode(DUV-LED)epitaxial structure is realized on the strain-free AlN template with Gr.Furthermore,the DUV-LED with Gr demonstrate 2.1 times enhancement of light output power and a better stability of luminous wavelength compared to that on bare sapphire.An in-depth understanding of this work reveals diverse beneficial impacts of Gr on nitride growth and provides a novel strategy of relaxing the vital requirements of hetero-mismatch in conventional heteroepitaxy.
基金the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)under Germany’s Excellence Strategy via the Excellence Cluster 3D Matter Made to Order(EXC-2082/1-390761711)through the DFG priority program SPP 1839“Tailored disorder”.
文摘Owing to their high color purity,tunable bandgap,and high efficiency,quantum dots(QDs)have gained significant attention as color conversion materials for high-end display applications.Moreover,inkjet-printed QD pixels show great potential for realizing full-color mini/micro-light emitting diode(micro-LED)-based displays.As a color conversion layer,the photoluminescence intensity of QDs is limited by the insufficient absorptance of the excitation light due to the lack of scattering.Conventional scatterers,such as titanium dioxide microparticles,have been applied after additional surface engineering for sufficient dispersity to prevent nozzle clogging in inkjet printing process.In our work,as an alternative approach,we use inkjet printing for depositing a phase separating polymer ink based on polystyrene(PS)and polyethylene glycol(PEG).QD/polymer composite pixels with scattering micropores are realized.The morphology of the micropores can be tailored by the weight ratio between PS and PEG which enables the manipulation of scattering capability.With the presence of the microporous structure,the photoluminescence intensity of the QD film is enhanced by 110%in drop-cast films and by 35.3%in inkjet-printed QD pixel arrays compared to the reference samples.
基金the financial support provided by CONACYT(grant no.CB-2014-1-241458)the Nanosensors and Devices Research Group at Tecnologico de Monterrey(0020209I06).
文摘The introduction of two-photon polymerization(TPP)into the area of Carbon Micro Electromechanical Systems(CMEMS)has enabled the fabrication of three-dimensional glassy carbon nanostructures with geometries previously unattainable through conventional UV lithography.Pyrolysis of TPP structures conveys a characteristic reduction of feature size—one that should be properly estimated in order to produce carbon microdevices with accuracy.In this work,we studied the volumetric shrinkage of TPP-derived microwires upon pyrolysis at 900℃.Through this process,photoresist microwires thermally decompose and shrink by as much as 75%,resulting in glassy carbon nanowires with linewidths between 300 and 550 nm.Even after the thermal decomposition induced by the pyrolysis step,the linewidth of the carbon nanowires was found to be dependent on the TPP exposure parameters.We have also found that the thermal stress induced during the pyrolysis step not only results in axial elongation of the nanowires,but also in buckling in the case of slender carbon nanowires(for aspect ratios greater than 30).Furthermore,we show that the calculated residual mass fraction that remains after pyrolysis depends on the characteristic dimensions of the photoresist microwires,a trend that is consistent with several works found in the literature.This phenomenon is explained through a semi-empirical model that estimates the feature size of the carbon structures,serving as a simple guideline for shrinkage evaluation in other designs.
基金funded by the Federal Ministry of Education and Research of Germany in the framework of PANAMAT(project number 03XP0161)the Ministry of Science,Research and Arts of the state of Baden Wurttemberg through the MERAGEM graduate school+1 种基金supported by the German Federal Environmental Foundation(Deutsche Bundesstiftung Umwelt-DBU)through the DBU PhD scholarship programThis project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 814945-SolBio-Rev.
文摘Energy-harvesting from low-temperature environmental heat via thermoelectric generators(TEG)is a versatile and maintenancefree solution for large-scale waste heat recovery and supplying renewable energy to a growing number of devices in the Internet of Things(IoT)that require an independent wireless power supply.A prerequisite for market competitiveness,however,is the costeffective and scalable manufacturing of these TEGs.Our approach is to print the devices using printable thermoelectric polymers and composite materials.We present a mass-producible potentially low-cost fully screen printed flexible origami TEG.Through a unique two-step folding technique,we produce a mechanically stable 3D cuboidal device from a 2D layout printed on a thin flexible substrate using thermoelectric inks based on PEDOT nanowires and a TiS2:Hexylamine-complex material.We realize a device architecture with a high thermocouple density of 190 per cm2 by using the thin substrate as electrical insulation between the thermoelectric elements resulting in a high-power output of 47.8μWcm^(−2)from a 30 K temperature difference.The device properties are adjustable via the print layout,specifically,the thermal impedance of the TEGs can be tuned over several orders of magnitudes allowing thermal impedance matching to any given heat source.We demonstrate a wireless energy-harvesting application by powering an autonomous weather sensor comprising a Bluetooth module and a power management system.
基金supported by the German Federal Ministry of Education and Research(BMBF)through Grant FKZ:03INT606AGas well as the Deutsche Forschungsgemeinschaft(DFG)via the Excellence Cluster“3D Matter Made to Order”(EXC-2082/1-390761711)supported by Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(2021R1A6A3A03044559).
文摘Upcoming technologies in the fields of flexible electronics require the cost-efficient fabrication of complex circuitry in a streamlined process.Digital printing techniques such as inkjet printing can enable such applications thanks to their inherent freedom of design permitting the mask-free deposition of multilayer optoelectronic devices without the need for subtracting techniques.Here we present an active matrix sensor array comprised of 100 inkjet-printed organic thin film transistors(OTFTs)and organic photodiodes(OPDs)monolithically integrated onto the same ultrathin substrate.Both the OTFTs and OPDs exhibited high-fabrication yield and state-of-the-art performance after the integration process.By scaling of the OPDs,we achieved integrated pixels with power consumptions down to 50 nW at one of the highest sensitivities reported to date for an all-organic integrated sensor.Finally,we demonstrated the application potential of the active matrix by static and dynamic spatial sensing of optical signals.
基金the German Federal Ministry of Education and Research(BMBF)under contract 03EK3501H(project POPUP)The AFM was made available through funding by the BMBF,grant no.03EK3504(Project TAURUS)the Center for Functional Nanostructures(CFN).
文摘Ternary absorber blends have recently been identified as promising concepts to spectrally broaden the absorption of organic bulkheterojunction solar cells and hence to improve their power conversion efficiencies.In this work,we demonstrate that D-D-A ternary blends comprising two donor polymers and the acceptor PC61BM can also significantly enhance the thermal stability of the solar cell.Upon harsh thermal stress at 120°C for 2 h,the ternary solar cells show only a minor relative deterioration of 10%.Whereas the polymer/fullerene blend PTB7-Th:PC61BM is rather unstable under these conditions,its degradation was efficiently suppressed by incorporating the near infrared-absorbing polymer PDTP–DFBT.Spectroscopic ellipsometry investigations and an effective medium analysis of the ternary absorber blend revealed that the domain conformation in presence of PDTP–DFBT remains stable whereas the domain conformation changes in its absence.The ternary PTB7-Th:PDTP–DFBT:PC61BM solar cells yield thermally stable power conversion efficiencies of up to 6%.
基金the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)under Germany’s Excellence Strategy via the Excellence Cluster 3D Matter Made to Order(EXC-2082/1-390761711)by BMBF within the funding for the programme Forschungslabore Mikroelektronik Deutschland(ForLab)。
文摘X-ray detectors are of pivotal importance for the scientific and technological progress in a wide range of medical,industrial,and scientific applications.Here,we take advantage of the printability of perovskite-based semiconductors and achieve a high X-ray sensitivity combined with the potential of an exceptional high spatial resolution by our origami-inspired folded perovskite X-ray detector.The high performance of our device is reached solely by the folded detector architecture and does not require any photolithography.The design and fabrication of a foldable perovskite sensor array is presented and the detector is characterized as a planar and as a folded device.Exposed to 50 kVp−150 kVp X-ray radiation,the planar detector reaches X-ray sensitivities of 25−35μC/(Gyaircm^(2)),whereas the folded detector achieves remarkably increased X-ray sensitivities of several hundredμC/(Gyaircm^(2))and a record value of 1409μC/(Gyaircm^(2))at 150 kVp without photoconductive gain.Finally,the potential of an exceptional high spatial resolution of the folded detector of more than 20 lp/mm under 150 kVp X-ray radiation is demonstrated.
基金The work was supported by the National Key R&D Program of China(2019YFA0708200)the National Natural Science Foundation of China(T2188101,52125307,52021006 and 12074369)+1 种基金the“2011 Program”from the Peking-Tsinghua-IOP Collaborative Innovation Center of Quantum Matter,Youth Innovation Promotion Association,CASthe Youth Supporting Program of Institute of Semiconductors.
文摘Heteroepitaxy can reduce the cost and widen the application range of semiconductor film synthesis and device fabrication.However,the lattice and thermal expansion coefficient mismatches between epilayers and substrates limit the improvement of crystal quality and device performance.Two-dimensional(2D)material-assisted heteroepitaxy offers an effective solution to these challenges.The weak interaction at the interface between films and substrates facilitates the subsequent exfoliation and transfer of epilayer for the fabrication of flexible or high-power electronics.Herein,we summarize the modes of 2D material-assisted epitaxy,which can be classified into remote epitaxy,pinhole epitaxy and van der Waals epitaxy based on the interfacial interaction between the epilayers and substrates.Furthermore,we discuss in detail the improved crystal quality and functional applications,such as flexible devices,wavelength-modulated optoelectronic devices,and thermal management in high-power devices.Moreover,we highlight the challenges and prospects of 2D material-assisted epitaxy,providing roadmaps for lateral research and semiconductor production.
