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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Identification and Characterization of ‘Killer-Modes’ in Organic Semiconductors with Terahertz Spectroscopy
摘要： Organic semiconductors are promising modern optoelectric materials, with countless potential applications ranging from ?exible displays to photovoltaics. The applicability of these materials is largely driven by their charge carrier mobility, which is strongly in?uenced by low-frequency vibrations. In this work, the speci?c low-frequency vibrations that exhibit strong electron-phonon coupling, deemed ‘killer-modes’, in organic semiconductors are determined using a combination of terahertz time-domain spectroscopy and solid-state density functional theory. The results of this study enable a concerted synthetic effort to rationally design novel materials, utilizing intermolecular forces to stiffen lattice dynamics, to ultimately improve charge carrier mobility.
关键词： electron-phonon coupling,organic semiconductors,charge carrier mobility,solid-state density functional theory,terahertz spectroscopy
更新于2025-09-11 14:15:04
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Effects of energy and hydrogen peroxide concentration on structural and optical properties of CuO nanosheets prepared by pulsed laser ablation
摘要： Laser ablation of copper targets using Ce:Nd:YAG laser with pulses of 1064 nm wavelengths at 10 ns pulse width and with different laser pulse energies and in different concentrations of H2O2 solution is investigated experimentally. Cu/CuO flake-like nanostructures with visible band gap and the extension of its light absorption by changing the synthesis parameters such as laser pulse energy and concentration of H2O2 solution were observed. Characterization and comparison of the obtained suspensions are exploited by X-ray diffraction (XRD), UV–vis spectroscopy and field emission scanning electron microscopy (FE-SEM). The XRD analysis data show that in 10 vol% H2O2 solution CuO phase has been synthesized, while with decreasing the H2O2 concentration, Cu phase is also observed. The mean crystallite sizes of CuO were estimated using XRD patterns and were between 2.1 and 3.3 nm. The comparison of the UV–visible absorption spectra indicates that with decreasing pulse energy and decreasing H2O2 concentration up to 5 vol% the band gap of nanoparticles increased from 2.19 eV to 2.34 eV, which is accordant with the quantum confinement effect. FESEM image of all the synthesized samples illustrate the formation of flake-like nanostructure with the thickness of about 12–15 nm.
关键词： Oxides,Nanostructures,Semiconductors,Optical properties,Laser ablation
更新于2025-09-11 14:15:04
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Dot size variability induced changes in the optical absorption spectra of interdiffused quantum dot systems
摘要： In this work, we have quantified the effects of dot size variability on the interband optical absorption spectra of interdiffused III–V quantum dot (QD) systems through analytical models which agree well with experimental data. The variability function induced due to inhomogeneous nature of dot size distribution has been considered to be Gaussian in nature, where individual dots have been assumed to be lens-shaped having inhomogeneous material composition inside the dot. This is necessary to consider any realistic interdiffused system. Such an assumption is not in line-up with the conventional methodologies reported earlier on the subject, where the QD composition was considered to be homogeneous, presenting an ideal or quasi-ideal situation which may be applicable only for dot structures in absence of interdiffusion. Moreover, for the first time, the effects of dot size variability and interdiffusion on the optical spectra of QD systems have been analysed in the same platform. The effects of dot size deviation, QD aspect ratio, core group III content inside the dot, standard deviation, and so on, on the optical absorption spectra have been demonstrated.
关键词： Dot size variability,III–V semiconductors,Optical absorption spectra,Interdiffusion,Quantum dots
更新于2025-09-11 14:15:04
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Voltage-assisted SILAR deposition of CdSe quantum dots into mesoporous TiO2 film for quantum dot-sensitized solar cells
摘要： CdSe quantum dots (QDs) grows slowly in mesoporous TiO2 film deriving from a large lattice mismatch (11 %) and poor interaction between the two, which resulting the low power conversion efficiency (PCE) of quantum dot-sensitized solar cells (QDSSCs). An external voltage is applied in the successive ionic layer adsorption reaction (SILAR) process, which drives the Cd2+ and SeSO3 2- ions quickly diffused into the mesoporous TiO2 film and reacted to form CdSe QDs at room temperature. The CdSe QDSSCs yields a PCE of 3.27%. This work provides an efficient strategy to assemble QDs for enhancing the performance of QDSSCs.
关键词： Electrodeposition,Semiconductors,Energy storage and conversion,Solar energy materials,Nanoparticles
更新于2025-09-11 14:15:04
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Synthesis and characterization of vinazene end capped dipyrrolo[2,3-b:2′,3′-e]pyrazine-2,6(1H,5H)-dione small molecules as non-fullerene acceptors for bulk heterojunction organic solar cells
摘要： Two dipyrrolo[2,3-b:2',3'-e]pyrazine-2,6(1H,5H)-dione (PzDP)-based small molecules DPDV and DPEV with PzDP as the core building block and 4,5-dicyano-2-vinylimdazole (vinazene) as end-cap units were synthesized by Heck coupling reaction. The photophysical, electrochemical properties of DPDV and DPEV were investigated and applied as non-fullerene acceptors (NFAs) for solution-processed bulk heterojunction (BHJ) organic solar cells (OSCs). Theoretically evaluated optical and electrochemical properties were well matched with experimental values. Solution processed BHJOSCs employing poly[(4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl)-alt-(3-fluoro-2-[(2-ethylhexy)carbonyl]thieno[3,4-b]thiophene-4,6-diyl)] (PTB7) as the donor polymer and DPDV/ DPEV as NFAs exhibited short-circuit current density (JSC) of 2.23/ 2.44 mA cm-2, open-circuit voltage (VOC) of 0.54/ 0.55 V, fill factor (FF) of 36.97/ 38.62 and power conversion efficiency (PCE) of 0.45/0.52%, respectively.
关键词： heterocycles,cyclic voltammetry,bulk heterojunction organic solar cells,non-fullerene acceptors materials,organic semiconductors
更新于2025-09-11 14:15:04
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Ultraviolet radiation-induced photovoltaic action in γ-CuI/β-Ga2O3 heterojunction
摘要： We report on the fabrication of γ-phase copper iodide (γ-CuI) and beta-gallium oxide (β-Ga2O3) heterostructure device and obtaining the ultraviolet (UV) radiation responsive photovoltaic action. The crystalline γ-CuI with predominant (111) plane orientation was deposited on the β-Ga2O3 by thermal evaporation process under vacuum condition. The electrical analysis revealed that the γ-CuI/β‐Ga2O3 heterojunction possess an excellent rectifying diode characteristic with high rectification ratio and turn-on voltage. The fabricated heterojunction device showed a photovoltaic action under solar-blind UV irradiation (254 nm) with outstanding photovoltage of 0.706 V and photocurrent of 2.49 mA/W. The device also showed a photovoltaic action under illumination of 365 nm and 300-400 nm wavelength of UV light, corresponding to absorption due to the γ-CuI layer. The UV irradiation-induced photovoltaic action in the γ-CuI/β‐Ga2O3 with outstanding photovoltage and excellent diode characteristics can be significant for self-powered UV photodetector applications.
关键词： Semiconductors,Electrical properties,Photovoltaic action,Copper iodide,Beta-gallium oxide,Solar-blind radiation
更新于2025-09-11 14:15:04
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Optoelectronics - Advanced Device Structures || Hybrid Silicon-Organic Heterojunction Structures for Photovoltaic Applications
摘要： The concept for inorganic-organic device is an attractive technology to develop devices with better characteristics and functionality due to the complementary advantages of inorganic and organic materials. This chapter provides an overview of the principal requirements for organic and inorganic semiconductor properties and their fabrication processes and focus on the compatibility between low temperature plasma enhanced chemical vapor deposition (PECVD) and polymer organic materials deposition. The concept for inorganic-organic device was validated with the fabrication of three hybrid thin film photovoltaic structures, based on hydrogenated silicon (Si:H), organic poly(3-hexythiophene): methano-fullerenephenyl-C61-butyric-acid-methyl-ester (P3HT:PCBM), and poly(3,4ethylenedioxythiophene): poly(4-styrenesulfonate) (PEDOT:PSS) films. Optoelectronic characteristics, performance characteristics, and interfaces of the different configurations aspects are discussed. Hybrid ITO/PEDOT:PSS/(i)Si:H/(n)Si:H structure results in a remarkably high short circuit current density as large as 17.74 mA/cm2, which is higher than the values in organic or inorganic reference samples. Although some hybrid structures demonstrated substantial improvement of performance, other hybrid structures showed poor performance, further R&D efforts seem to be promising, and should be focused on deeper study of organic materials and related interface properties.
关键词： thin film devices,hybrid devices,plasma deposited materials,solar cells,organic semiconductors
更新于2025-09-11 14:15:04
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Reply to: Can lasers really refrigerate CdS nanobelts?
摘要： Five years ago, Xiong and co-workers reported the net laser cooling of a CdS nanobelt1, which seemed to be the remarkable conclusion to a 16-year search for ways to successfully cool a semiconductor using light2,3. However, as we describe below, there are questions and concerns about this study that cast doubts on its validity.
关键词： optical refrigeration,CdS nanobelts,semiconductors,laser cooling
更新于2025-09-11 14:15:04
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Coupling heterostructure of thickness-controlled nickel oxide nanosheets layer and titanium dioxide nanorod arrays via immersion route for self-powered solid-state ultraviolet photosensor applications
摘要： A coupling heterostructure consisting of nickel oxide nanosheets (NNS) and titanium dioxide nanorod arrays (TNAs) was fabricated for self-powered solid-state ultraviolet (UV) photosensor applications. By controlling the thickness of the NNS layer by via varying the growth time from 1 to 5 h at a deposition temperature of 90 °C, the coupling NNS/TNAs heterojunction films were formed and their structural, optical, electrical and UV photoresponse properties were investigated. The photocurrent measured from the fabricated self-powered UV photosensor was improved by increasing the thickness of NNS from 140 to 170 nm under UV irradiation (365 nm, 750 mWcm?2) at 0 V bias. A maximum photocurrent density of 0.510 mA?cm?2 was achieved for a sample with a NNS thickness of 170 nm and prepared with a 3 h NNS growth time. Our results showed that the fabricated NNS/TNAs heterojunction has potential applications for self-powered UV photosensors.
关键词： TiO2 nanorods,Electronic materials,Semiconductors,Immersion route,Photosensor,NiO nanosheets
更新于2025-09-11 14:15:04
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[IEEE 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Ottawa, ON, Canada (2019.7.8-2019.7.12)] 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Model Calibration of InGaAs/InP p-I-n Test Structures
摘要： Numerical calibration of InGaAs/InP double-heterostructure p-I-n junctions is performed at room temperature using guarded test structures of various areas and investigating the contributions from minority carrier diffusion, depletion region generation and finally perimeter (shunt) leakage. The perimeter leakage is determined to be 0.5 pA/cm, whereas the depletion region contributes 2.2 nA/cm2; the bulk diffusion contribution is excluded via the guard ring but can be computed analytically to be 2.0 nA/cm2. Reproducing the experimental test structures within the numerical modeling environment accurately reproduces the data based on calibrating the diffusion length and SRH lifetime.
关键词： dark current,III-V semiconductors,diffusion length,perimeter leakage,recombination
更新于2025-09-11 14:15:04