Fabrication of PdSe2/GaAs Heterojunction for Sensitive Near-Infrared Photovoltaic Detector and Image Sensor Application

In this study,we have developed a high-sensitivity,near-infrared photodetector based on PdSe2/GaAs heterojunction,which was made by transferring a multilayered PdSe2 film onto a planar GaAs.The as-fabricated PdSe2/GaAs heterojunction device exhibited obvious photovoltaic behavior to 808 nm illumination,indicating that the near-infrared photodetector can be used as a self-driven device without external power supply.Further device analysis showed that the hybrid heterojunction exhibited a high on/off ratio of 1.16×10^5 measured at 808 nm under zero bias voltage.The responsivity and specific detectivity of photodetector were estimated to be 171.34 mA/W and 2.36×10^11 Jones,respectively.Moreover,the device showed excellent stability and reliable repeatability.After 2 months,the photoelectric characteristics of the near-infrared photodetector hardly degrade in air,attributable to the good stability of the PdSe2.Finally,the PdSe2/GaAs-based heterojunction device can also function as a near-infrared light sensor.

High efficiency ETM-free perovskite cell composed of CuSCN and increasing gradient CH_(3)NH_(3)PbI_(3)

To enhance device performance and reduce fabrication cost,a series of electron transporting material(ETM)-free perovskite solar cells(PSCs)is developed by TCAD Atlas.The accuracy of the physical mode of PSCs is verified,due to the simulations of PEDOT:PSS-CH_(3)NH_(3)PbI_(3)-PCBM and CuSCN-CH_(3)NH_(3)PbI_(3)-PCBM p-i-n PSCs showing a good agreement with experimental results.Different hole transporting materials(HTMs)are selected and directly combined with n-CH_(3)NH_(3)PbI_(3),and the CuSCN-CH_(3)NH_(3)PbI_(3) is the best in these ETM-free PSCs.To further study the CuSCN-CH_(3)NH_(3)PbI_(3) PSC,the influences of back electrode material,gradient band gap,thickness,doping concentration,and bulk defect density on the performance are investigated.Energy band and distribution of electric field are utilized to optimize the design.As a result,the efficiency of CuSCN-CH_(3)NH_(3)PbI_(3) PSC is achieved to be 26.64%.This study provides the guideline for designing and improving the performances of ETM-free PSCs.

Non-ultrawide bandgap CsPbBr_(3) nanosheet for sensitive deep ultraviolet photodetection

In this study,we report the fabrication of a sensitive deep ultraviolet(DUV)photodetector by using CsPbBr_(3) nanosheets synthesized through confined-space growth at room temperature.The peak pho-toresponse of the device upon illumination blueshifts with decreasing thickness and a 68 nm CsPbBr_(3) nanosheet based device displays a peak response to 265 nm illumination,showing responsivity and spe-cific detectivity of 85 mA/W and 4.05×1011 Jones at 3 V bias,respectively.Theoretical simulation re-veals that the blueshift is associated with the wavelength-dependent absorption coefficient of CsPbBr_(3) nanosheet:incident light with shorter wavelengths can be absorbed on the superficial surface,while long-wavelength light has a larger penetration depth,leading to dominant DUV absorption in thinner CsPbBr_(3) nanosheet.This work will shed light on the facile and cost-effective fabrication of DUV photode-tectors from non-ultrawide bandgap(UWBG)all-inorganic perovskite materials.

Interfacial state induced ultrasensitive ultraviolet light photodetector with resolved flux down to 85 photons per second

We present an ultrasensitive ultraviolet （UV） detector based on a p-type ZnS nanoribbon （NR）/indium tin oxide （ITO） Schottky barrier diode （SBD）. The device exhibits a pseudo-photovoltaic behavior which can allow the SBD to detect UV light irradiation with incident power of 6 × 10^-17 W （-85 photons/s on the NR） at room temperature, with excellent reproducibility and stability. The corresponding detectivity and photoconductive gain are calculated to be 3.1 × 10^20 cm.Hz1/2.W^-1 and 6.6 × 10^5, respectively. It is found that the presence of the trapping states at the p-ZnS NWITO interface plays a crucial role in determining the ultrahigh sensitivity of this nanoSBDs. Based on our theoretical calculation, even ultra-low photon fluxes on the order of several tens of photons could induce a significant change in interface potential and consequently cause a large photocurrent variation. The present study provides new opportunities for developiphigh-performance optoelectronic devices in the future.

Nanochannel-confined growth of crystallographically orientated perovskite nanowire arrays for polarization-sensitive photodetector application

Highly ordered perovskite nanowire(PNW)arrays are important building blocks for potential application in integrated optoelectronic devices due to their unique properties.Herein,a recordable digital versatile disk-assisted nanochannel-confined growth(NCG)strategy was developed for large-scale growth of different kinds of PNW arrays with preferentially crystallographic orientation on various substrates.Photodetector constructed from MAPb I3 NW arrays exhibits prominent photoresponse properties with a responsivity of 20.56 A W^(-1) and specific detectivity of 4.73×10^(12) Jones,respectively.What is more,the photodetector can function as a polarization-sensitive photodetector due to the crystallographic orientation of the one-dimensional PNW arrays,with a polarization ratio of 2.2.The proposed NCG strategy provides a cost-efficient and effective method for the fabrication of high-quality PNW arrays with potential applications in future integrated devices and systems.

1D/2D material-based photodetectors driven by ferroelectrics

One-dimensional （1D） and two-dimensional （2D） materials, such as nanowires, graphene, and transition metal dichalcogenides （TMDs）, have received emerging research study in the past ten years [1-3]. They have demonstrated to be idea building blocks for fabricating high-performance photodetector devices owing to their unique electrical and optical properties [4-6].