Two-dimensional(2D)semiconductors with intrinsic ferromagnetism are highly desirable for potential applications in nextgeneration spintronic and optoelectronic devices.However,controllable synthesis of intrinsic 2D magnetic semiconductor on a substrate is still a challenging task.Herein,large-area 2D non-layered rock salt(α-phase)MnSe nanosheets were grown on mica substrates,with the thickness changing from 54.2 to 0.9 nm(one unit cell),by chemical vapour deposition.The X-ray diffraction,Raman spectroscopy,transmission electron microscopy,and X-ray photoelectron spectroscopy measurements confirmed that the resulting 2Dα-MnSe nanosheets were obtained as high-quality single crystals.The magnetic hysteresis loops and synchrotron X-ray measurements directly indicated the anomalous magnetic properties inα-MnSe nanosheets.Comprehensive analysis of the reasons for magnetic property revealed that the low-temperature phase transition,small number of stacking differences in crystals,and surface weak oxidation in(111)-orientedα-MnSe were the main mechanisms.Furthermore,α-MnSe nanosheets exhibited broadband photoresponse from 457 to 671 nm with an outstanding detectivity and responsivity behaviours.This study presents the detailed growth process of ultrathin 2D magnetic semiconductorα-MnSe,and its outstanding magnetic properties and broadband photodetection,which provide an excellent platform for magneto-optical and magneto-optoelectronic research.
Ye ZhaoRuilong YangKe YangJiarui DouXiaoting YangJinzhong GuoGuowei ZhouXiaohong Xu
It remains full of challenge for extending short-wave infrared(SWIR)spectral response and weak-light detection in the context of broad spectral responses for phototransistor.In this work,a novel poly(2,5-bis(4-hexyldodecyl)-2,5-dihydro-3,6-di-2-thienyl-pyrrolo[3,4-c]pyrrole-1,4-dione-alt-thiophene)(PDPPT3-HDO):COTIC-4F organic bulk-heterojunction is prepared as active layer for bulk heterojunction phototransistors.PDPPT3-HDO serves as a hole transport material,while COTIC-4F enhances the absorption of SWIR light to 1020 nm.As a result,smooth and connected PDPPT3-HDO film is fabricated by blade coating method and exhibits high hole mobility up to 2.34 cm^(2)·V^(-1)·s^(-1) with a current on/off ratio of 4.72×10^(5) in organic thin film transistors.PDPPT3-HDO:COTIC-4F heterojunction phototransistors exhibit high responsivity of 2680 A·W^(-1) to 900 nm and 815 A·W^(-1) to 1020 nm,with fast response time(rise time~20 ms and fall time~100 ms).The photosensitivity of the heterojunction phototransistor improves as the mass ratio of non-fullerene acceptors increases,resulting in an approximately two orders of magnitude enhancement compared to the bare polymer phototransistor.Importantly,the phototransistor exhibits decent responsivity even under ultra-weak light power of 43μW·cm^(-2) to 1020 nm.This work represents a highly effective and general strategy for fabricating efficient and sensitive SWIR light photodetectors.
Broadband photodetection,spanning from ultraviolet(UV)to infrared(IR),is pivotal in diverse technological domains including astronomy,remote sensing,environmental monitoring,and medical diagnostics.However,current commercially available broadband photodetectors,predominately based on conventional narrow-bandgap semiconductors,exhibit limited sensitivity in the UV region.This limitation,stemming from the significant energy disparity between the semiconductor bandgap and UV photon,narrows their application scope.Herein,we report an innovative approach involving the in-situ van der Waals(vdW)integration of two-dimensional(2D)GeSe_(2)layers onto a Si substrate.This process yields a high-quality GeSe_(2)/Si vdW heterojunction device,which features a broad response range covering from UV to near-IR(NIR)with a greatly-enhanced sensitivity in the UV region.The device possesses high responsivities of 325 and 533.4 mA/W,large detectivities of 1.24×10^(13)and 2.57×10^(13)Jones,and fast response speeds of 20.6/82.1 and 17.7/81.0μs under 360 and 980 nm,respectively.Notably,the broadband image sensing and secure invisible optical communication capabilities of the GeSe_(2)/Si heterojunction device are demonstrated.Our work provides a viable approach for UV-enhanced broadband photodetection technology,opening up new possibilities and applications across various scientific and technological domains.
This study attempts to develop a reproducible thin-film formation technique called vacuum-free(VF)lamination,which transfers thin films using elastomeric polymer-based laminating mediators.Precisely,by controlling the interface characteristics of the mediator based on the work of adhesion,VF lamination is successfully performed for various thicknesses(from 20 to 240 nm)of a conjugated photoactive material composed of poly[(2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro)thiophen-2-yl)-benzo[1,2-b:4,5-bʹ]dithiophene))-alt-(5,5-(1ʹ,3ʹ-di-2-thienyl-5ʹ,7ʹ-bis(2-ethylhexyl)benzo[1ʹ,2ʹ-c:4ʹ,5ʹ-cʹ]dithiophene-4,8-dione)](a polymer donor)and 2,2ʹ-((2Z,2ʹZ)-((12,13-bis(2-butyloctyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2ʹʹ,3ʹʹ:4ʹ,5ʹ]thieno[2ʹ,3ʹ:4,5]pyrrolo[3,2-g]thieno[2ʹ,3ʹ:4,5]thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile(a nonfullerene acceptor).Interestingly,the organic photovoltaic and photodetecting applications,prepared by the VF lamination process,showed superior performance compared to those of devices prepared by conventional spin-coating.This is due to the overturned surface morphology,which led to enhanced charge transport ability and blocking of the externally injected charge.Thus,the reproducible VF lamination process,exploiting an adhesion-based elastomeric polymer mediator,is a promising thin-film formation technique for developing efficient next-generation organic optoelectronic materials consistent with the solution process.
Narrowband photodetection is an important measurement technique for material analysis and sensing,for example,nondispersive infrared sensing technique.Both photoactive material engineering and nanophotonic filtering schemes have been explored to realize wavelength-selective photodetection,while most devices have a responsive bandwidth larger than 2%of the operating wavelength,limiting sensing performance.Near-infrared photodetection with a bandwidth of less than 0.2%of the operating wavelength was demonstrated experimentally in Au/Si Schottky nanojunctions.A minimum linewidth of photoelectric response down to 2.6 nm was obtained at a wavelength of 1550 nm by carefully tailing the absorptive and radiative loss in the nanostructures.Multiple functions were achieved on chip with the corrugated Au film,including narrowband resonance,light harvesting for sensing and photodetection,and electrodes for hot electron emission.Benefiting from such a unity integration with in situ photoelectric conversion of the optical sensing signal and the ultranarrowband resonance,self-contained on-chip biosensing via simple intensity interrogation was demonstrated with a limit of detection down to 0.0047%in concentration for glucose solution and 150 ng∕m L for rabbit IgG.Promising potential of this technique is expected for the applications in on-site sensing,spectroscopy,spectral imaging,etc.
The discovery of semiconductor has witnessed remarkable strides toward high performance of photodetectors attributed to its excellent carrier properties.However,semimetal,owning to the high carrier concentration and low carrier mobility compared to those of semiconductor,is generally considered unsuitable for photodetection.Herein,we demonstrate an outstanding photodetection in a layered semimetal titanium diselenide(TiSe_(2))in Bose-Einstein condensation(BEC)state.High sensitivity of semimetal photodetector is realized in the range of visible,infrared and terahertz bands.The noise equivalent power(NEP)has threefold improvement at the visible and infrared wavebands,and significant decrease by one order of magnitude in the terahertz frequencies via BEC phenomenon,attributed to the electrical parameter variation after condensation.The best NEP value in the terahertz frequency is comparable to that of commercial Si photodetector.Our results show another recipe to fabricate high performance of photodetection via semimetal except for semiconductor and pave the way to exploit macroscopic quantum phenomena for optoelectronics.
Detecting light from a wealth of physical degrees of freedom(e.g.wavelength,intensity,polarization state,phase,etc)enables the acquirement of more comprehensive information.In the past two decades,low-dimensional van der Waals materials(vdWMs)have established themselves as transformative building blocks toward lensless polarization optoelectronics,which is highly beneficial for optoelectronic system miniaturization.This review provides a comprehensive overview on the recent development of low-dimensional vdWM polarized photodetectors.To begin with,the exploitation of pristine 1D/2D vdWMs with immanent in-plane anisotropy and related heterostructures for filterless polarization-sensitive photodetectors is introduced.Then,we have systematically epitomized the various strategies to induce polarization photosensitivity and enhance the degree of anisotropy for low-dimensional vdWM photodetectors,including quantum tailoring,construction of core–shell structures,rolling engineering,ferroelectric regulation,strain engineering,etc,with emphasis on the fundamental physical principles.Following that,the ingenious optoelectronic applications based on the low-dimensional vdWM polarized photodetectors,including multiplexing optical communications and enhanced-contrast imaging,have been presented.In the end,the current challenges along with the future prospects of this burgeoning research field have been underscored.On the whole,the review depicts a fascinating landscape for the next-generation high-integration multifunctional optoelectronic systems.
Yuhang MaHuaxin YiHuanrong LiangWan WangZhaoqiang ZhengJiandong YaoGuowei Yang
High-performance photodetectors hold promising potential in optical communication and imaging systems.However,conventional counterparts are suffering narrow detection range,high power consumption,and poor polarization sensitivity.Characteristics originating from switchable polarization in ferroelectrics can be used to optimize the photo-to-electric procedure and improve the photodetection performance.In this regard,we constructed a configuration by integrating 2-dimensional molybdenum disulfide(MoS_(2))with ferroelectric lithium niobate(LiNbO_(3)),resulting in the MoS_(2)/LiNbO_(3)heterostructured photodetector.Benefiting from the pyroelectric effect of LiNbO_(3),the limitation of bandgap on the detection range can be broken,thus broadening the response band of the detector to 365 to 1,064 nm,as well as enabling the self-powered characteristic.Meanwhile,high carrier mobility and decent light absorbance of MoS_(2)introduce robust light-matter interactions with the underlying LiNbO_(3),leading to ultrafast rise/fall times of≈150μs/250μs and switching ratios of up to≈190.Moreover,the highest responsivity,specific detectivity,and external quantum efficiency achieved were 17.3 A·W^(-1),4.3×10^(11)Jones,and 4,645.78%,respectively.Furthermore,because of the anisotropy of the spontaneous-polarized LiNbO_(3)substrate,the photocurrent of the device achieved a dichroic ratio of 7.42,comparing favorably to most MoS_(2)-based photodetectors.This work demonstrates the integration potential between ferroelectric LiNbO_(3)and 2-dimensional materials for high-performance photodetection.
