Mixed-dimensional composite structures using zero-dimensional(0D)quantum dots(QDs)and two-dimensional(2D)transition metal dichalcogenides(TMDs)materials are expected to attract great interest in optoelectronics due to the potential to generate new optical properties.Here,we report on the unique optical characteristics of a devices with mixed dimensional vertically stacked structures based on tungsten diselenide(WSe_(2))/CdSeS QDs monolayer/molybdenum disulfide(MoS_(2))(2D/0D/2D).Specifically,it exhibits an ambipolar photoresponse characteristic,with a negative photoresponse observed in the 400-600 nm wavelength range and a positive photoresponse appeared at 700 nm wavelength.It resulted in the high negative responsivity of up to 52.22 mA·W^(−1)under 400 nm,which is 163 times higher than that of the photodetector without CdSeS QDs.We also demonstrated the negative photoresponse,which could be due to increased carrier collision probability and non-radiative recombination.Device modeling and simulation reveal that Auger recombination among the types of non-radiative recombination is the main cause of negative photocurrent generation.Consequently,we discovered ambipolar photoresponse near a specific wavelength corresponding to the energy of quantum dots.Our study revealed interesting phenomenon in the mixed low-dimensional stacked structure and paved the way to exploit it for the development of innovative photodetection materials as well as for optoelectronic applications.
Young Jae ParkJaeho ShimJoo Song LeeKyu Seung LeeJi-Yeon KimKang Bok KoSang-Youp YimSeongjun KimHoon-Kyu ShinDonghee ParkYong Ju YunDong Ick Son
Self-powered full-spectrum photodetectors(PDs)offer numerous advantages,such as broad application fields,high precision,efficiency,and multi-functionality,which represent a highly promising and potentially valuable class of detectors for future development.However,insensitive response to solar-blind ultraviolet(UV)and complex and expensive preparation processes greatly limit their performance and practical application.In this study,a self-powered full-spectrum Bi_(2)Se_(3)/a-Ga_(2)O_(3)/p-Si heterojunction PD with high sensitivity for solar-blind UV band prepared by a simple and low-cost two-step synthesis method is presented.Experiments results reveal that the developed PD has an excellent performance,such as high sensitivity from 200 to 850 nm,and a responsivity of 1.38 mA/W as well as a detectivity of 3.22×10^(10) Jones under 254 nm light at zero bias.Additionally,the unencapsulated device displays exceptional stability and imaging capabilities.It is expected that Bi_(2)Se_(3)/a-Ga_(2)O_(3)/p-Si heterojunction PD with a simple and low-cost synthesis method has great potential for self-powered full-spectrum photodetectors.
Yajie HanShujie JiaoJiangcheng JingLei ChenPing RongShuai RenDongbo WangShiyong GaoJinzhong Wang
By combining the good charge transport property of graphene and the excellent photo-carrier generation char-acteristic of perovskite nanocrystal,we propose and demonstrate an ionic-gated synaptic transistor based on CsPbBr_(3)∕graphene heterojunction for bipolar photoresponse.Controlling the potential barrier of the CsPbBr_(3)∕graphene heterojunction by the ionic-gate of the electrical double-layer effect can promote the sepa-ration of photogenerated carriers and effectively retard their recombination.Using the ionic-gate-tunable Fermi level of graphene and the pinning effect of perovskite nanocrystal,the bipolar photocurrent responses correspond-ing to the excitatory and inhibitory short-term and long-term plasticity are realized by adjusting the negative gate bias.A series of synaptic functions including logic operation,Morse coding,the optical memory and electrical erasure effect,and light-assisted re-learning have also been demonstrated in an optoelectronic collaborative path-way.Furthermore,the excellent optical synaptic behaviors also contribute to the handwritten font recognition accuracy of-95%in artificial neural network simulations.The results pave the way for the fabrication of bipolar photoelectric synaptic transistors and bolster new directions in the development of future integrated human ret-inotopic vision neuromorphic systems.
Single wall carbon nanotube(SWCNT)/Si heterojunction photodetectors have the advantages of high photoresponse ability and simple structure,however,their detection wavelength range are usually lower than 1100 nm,which limits their application in the infrared band.We report a SWCNT/Cu/Si photodetector with both a high photoresponse and a detection range up to the infrared band by depositing a Cu nanoparticles(NPs)layer between a SWCNT film and a n-Si substrate.It was found that the Cu NPs produce strong surface plasmon resonance(SPR)under laser irradiation,which breaks through the limitation of Si band gap and greatly improves the photoresponse of the SWCNT/Cu/Si photodetector in the near infrared band.The responsivity(R)of the photodetector in the wavelength range of 1850–1200 nm reached 2.2–14.15 mA/W,which is the highest value in the reported plasmon enhanced n-Si based photodetectors,and about 20,000 times higher than that of a SWCNT/Si photodetector.Its R value for 1550 nm wavelength used in optical communications reached~8.2 mA/W,which is 64%higher than the previously reported values of commonly used photodetectors.We attribute the significant increase to the strong SPR and low Schottky barrier of Cu with n-Si,which facilitates the generation and transfer of the carriers.
Photoresponsive smart materials,which exhibit swift or instantaneous responses to external light stimuli,are pivotal for advancing the development of novel smart devices.Among these materials,photoresponsive tetracoordinate arylboron com-pounds emerge as prominent molecular systems,owing to their captivating photochemical mechanisms and photophysical transformations.In recent years,these molecules have experienced notable progress,leading to the emergence of numerous organic boron photoresponsive molecular systems with innovative structures and exceptional performance.In this comprehensive review,we present a thorough examination of the latest advancements in the field,systematically elucidating the design strategies and structure-activity relationships of these mol-ecules.Furthermore,we delve into the photoresponse mechanisms of various molecules and summarize their unique characteristics.Ultimately,we analyze the challenges,opportunities,and prospects encountered in this exciting field of research.
Jinjin WangMengzhen LiHaoyu GaoLixia XieXin ZhengGuoxing LiuTianjing WuLu LinLijie Liu
Orientation-dependent transport properties induced by anisotropic molecules are enticing in single-molecule junctions.Here,using the first-principles method,we theoretically investigate spin transport properties and photoresponse characteristics in trimesic acid magnetic single-molecule junctions with different molecular adsorption orientations and electrode contact sites.The transport calculations indicate that a single-molecule switch and a significant enhancement of spin transport and photoresponse can be achieved when the molecular adsorption orientation changes from planar geometry to upright geometry.The maximum spin polarization of current and photocurrent in upright molecular junctions exceeds 90%.Moreover,as the Ni tip electrode moves,the tunneling magnetoresistance of upright molecular junctions can be increased to 70%.The analysis of the spin-dependent PDOS elucidates that the spinterfaces between organic molecule and ferromagnetic electrodes are modulated by molecular adsorption orientation,where the molecule in upright molecular junctions yields higher spin polarization.Our theoretical work paves the way for designing spintronic devices and optoelectronic devices with anisotropic functionality base on anisotropic molecules.
Solar-blind ultraviolet(UV)photodetectors based on p-organic/n-Ga_(2)O_(3) hybrid heterojunctions have attracted extensive attention recently.Herein,the multifunctional solar-blind photodetector based on p-type poly[N-90-heptadecanyl-2,7-carbazole-alt-5,5-(40,70-di-2-thienyl-20,10,30-benzothiadiazole)](PCDTBT)/n-type amorphous Ga_(2)O_(3)(a-Ga_(2)O_(3))is fabricated and investigated,which can work in the phototransistor mode coupling with self-powered mode.With the introduction of PCDTBT,the dark current of such the a-Ga_(2)O_(3)-based photodetector is decreased to 0.48 pA.Meanwhile,the photoresponse parameters of the a-Ga_(2)O_(3)-based photodetector in the phototransistor mode to solar-blind UV light are further increased,that is,responsivity(R),photo-detectivity(D*),and external quantum efficiency(EQE)enhanced to 187 A W^(-1),1.3×10^(16) Jones and 9.1×10^(4)% under the weak light intensity of 11μW cm^(-2),respectively.Thanks to the formation of the built-in field in the p-PCDTBT/n-Ga_(2)O_(3) type-Ⅱ heterojunction,the PCDTBT/Ga_(2)O_(3) multifunctional photodetector shows self-powered behavior.The responsivity of p-PCDTBT/n-Ga_(2)O_(3) multifunctional photodetector is 57.5 mA W^(-1) at zero bias.Such multifunctional p-n hybrid heterojunction-based photodetectors set the stage for realizing high-performance amorphous Ga_(2)O_(3) heterojunction-based photodetectors.
