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Tuning Bandgap of Mixed-Halide Perovskite for Improved Photovoltaic Performance Under Monochromatic-Light Illumination
摘要： Organic–inorganic halide perovskites have emerged as promising materials for optoelectronic devices. This paper focuses on a new application field for perovskite materials as monochromatic-light conversion devices. First the optical properties of organic–inorganic perovskite semiconductors with bandgaps varying from near-infrared to visible at room temperature are presented. Two types of hybrid organic–inorganic mixed-halide perovskites, (FAPbI3)x(MAPbBr3)1-x and FA0.85MA0.15Pb(IxBr1-x)3, are adopted for bandgap tuning, an approximate linear variation of bandgaps with the x value is obtained. The relationship between thin film composition and device performance are investigated. Based on the results of the above bandgap tuning, two kinds of devices with bandgap near the wavelength of 683 nm are characterized under monochromatic-light illumination. A conversion efficiency of up to 40% under 60 mW cm?2 monochromatic-light illumination is achieved. The results confirm that the perovskite films exhibit sharp optical absorption edge, enabling highly efficient monochromatic-light conversion device.
关键词： monochromatic-light,hybrid mixed-halide perovskites,bandgap tuning,photovoltaic performance
更新于2025-11-25 10:30:42
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Steady Enhancement in Photovoltaic Properties of Fluorine Functionalized Quinoxaline-Based Narrow Bandgap Polymer
摘要： To investigate the influence of fluoride phenyl side-chains onto a quinoxaline (Qx) unit on the photovoltaic performance of the narrow bandgap (NBG) photovoltaic polymers, herein, two novel NBG copolymers, PBDTT-DTQx and PBDTT-DTmFQx, were synthesized and characterized. 2-ethylhexylthiothiophene-substituted benzodithiophene (BDTT), 2,3-diphenylquinoxaline (DQx) [or 2,3-bis(3-fluorophenyl)quinoxaline (DmFQx)] and 2-ethylhexylthiophene (T) were used as the electron donor (D) unit, electron-withdrawing acceptor (A) unit and π-bridge, respectively. Compared to non-fluorine substituted PBDTT-DTQx, fluoride PBDTT-DTmFQx exhibited a wide UV-Vis absorption spectrum and high hole mobility. An enhanced short-circuit current (Jsc) and fill factor (FF) simultaneously gave rise to favorable efficiencies in the polymer/PC71BM-based polymer solar cells (PSCs). Under the illumination of AM 1.5G (100 mW cm?2), a maximum power conversion efficiency (PCE) of 6.40% was achieved with an open-circuit voltage (Voc) of 0.87 V, a Jsc of 12.0 mA cm?2 and a FF of 61.45% in PBDTT-DTmFQx/PC71BM-based PSCs, while PBDTT-DTQx-based devices also exhibited a PCE of 5.43%. The excellent results obtained demonstrate that PBDTT-DTmFQx by fluorine atom engineering could be a promising candidate for organic photovoltaics.
关键词： quinoxaline,synthesis,polymer solar cells,bulk heterojunction,narrow bandgap conjugated polymer
更新于2025-11-19 16:56:42
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RbF post deposition treatment for narrow bandgap Cu(In,Ga)Se2 solar cells
摘要： Multi-junction solar cells are known to have a considerably increased efficiency potential over their typical single junction counterparts. In order to produce low cost and lightweight multi-junction devices, the availability of suitable narrow (<1.1 eV) bandgap bottom cells is paramount. A possible absorber for such a bottom cell is the Cu(In,Ga)Se2 (CIGS) compound semiconductor, one of the most efficient thin film materials to date. In this contribution we report on the RbF post deposition treatment of narrow bandgap CIGS absorbers grown with a single bandgap grading approach. We discuss the necessary deposition conditions and the observed improvements on solar cells performance. A certified record efficiency of 18.0 % for an absorber with 1.00 eV optoelectronic bandgap is presented and its suitability for perovskite/CIGS tandem devices is shown.
关键词： Post deposition treatment,Narrow bandgap,Tandem solar cells,Thin film solar cells,photovoltaics,Rubidium fluoride,Copper indium gallium selenide
更新于2025-11-14 17:28:48
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The characteristics of Cu(In, Ga)Se2 thin-film solar cells by bandgap grading
摘要： The performance of CIGSe-1 and CIGSe-2 absorber layers are compared with Eg grading such that a higher Ga content is incorporated into the back region. A wider depth range of the high-Ga region near the back of a CIGSe absorber layer can reduce its performance due to the increased formation of Ga-related defects and defect clusters. Therefore, for an Eg-graded CIGSe layer with a wider Eg on the back surface, appropriate Eg grading can improve its performance.
关键词： CIGSe,bandgap grading,defect,surface potential,solar cell
更新于2025-11-14 17:28:48
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Efficient Dye-Sensitized Solar Cells Composed of Nanostructural ZnO Doped with Ti
摘要： Photoanode materials with optimized particle sizes, excellent surface area and dye loading capability are preferred in good-performance dye sensitized solar cells. Herein, we report on an efficient dye-sensitized mesoporous photoanode of Ti doped zinc oxide (Ti-ZnO) through a facile hydrothermal method. The crystallinity, morphology, surface area, optical and electrochemical properties of the Ti-ZnO were investigated using X-ray photoelectron spectroscopy, transmission electron microscopy and X-ray diffraction. It was observed that Ti-ZnO nanoparticles with a high surface area of 131.85 m2 g?1 and a controlled band gap, exhibited considerably increased light harvesting efficiency, dye loading capability, and achieved comparable solar cell performance at a typical nanocrystalline ZnO photoanode.
关键词： bandgap energy,dye-sensitized solar cell,photovoltaic performance,Ti doped ZnO
更新于2025-11-14 17:04:02
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Achieving a high open-circuit voltage in inverted wide-bandgap perovskite solar cells with a graded perovskite homojunction
摘要： Wide-bandgap (~1.7-1.8 eV) perovskite solar cells have attracted substantial research interest in recent years due to their great potential to fabricate efficient tandem solar cells via combining with a lower bandgap (1.1-1.3 eV) absorber (e.g., Si, copper indium gallium diselenide, or low-bandgap perovskite). However, wide-bandgap perovskite solar cells usually suffer from large open circuit voltage (Voc) deficits caused by small grain sizes and photoinduced phase segregation. Here, we demonstrate that in addition to large grain sizes and passivated grain boundaries, controlling interface properties is critical for achieving high Voc’s in the inverted wide-bandgap perovskite solar cells. We adopt guanidinium bromide solution to tune the effective doping and electronic properties of the surface layer of perovskite thin films, leading to the formation of a graded perovskite homojunction. The enhanced electric field at the perovskite homojunction is revealed by Kelvin probe force microscopy measurements. This advance enables an increase in the Voc of the inverted perovskite solar cells from an initial 1.12 V to 1.24 V. With the optimization of the device fabrication process, the champion inverted wide-bandgap cell delivers a power conversion efficiency of 18.19% and sustains more than 72% of its initial efficiency after continuous illumination for 70 h without encapsulation. Additionally, a semitransparent device with an indium tin oxide back contact retains more than 88% of its initial efficiency after 100 h maximum power point tracking.
关键词： wide-bandgap perovskite solar cells,perovskite homojunction,guanidinium bromide
更新于2025-10-22 19:40:53
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Bandgap engineering of cobalt-doped bismuth ferrite nanoparticles for photovoltaic applications
摘要： The bandgap energy range of multiferroic bismuth ferrite is 2.2–2.7 eV, making it a promising candidate for photovoltaic (PV) applications. But its ef?ciency is still very low (<2%). This report thus focusses on the application of bismuth ferrite (BFO) engineered with cobalt (Co) doping and on the tuning of its bandgap energy (Eg). BiFeO3 is a unique multiferroic material that simultaneously displays both ferromagnetic and ferroelectric properties at room temperature. Co doped with pure BiFeO3 (BiFe(1?x)Cox O3; x = 0, 0.05, 0.1 and 0.15) was synthesized by the sol–gel method and annealed at 600?C. X-ray diffraction shows the well-arranged crystalline structure and peaks of pure and doped-BiFeO3 nanoparticles. A suitable reduction of Eg has been observed for Co-doped BiFeO3, which may be appropriate for the effective use in PV solar cells. Thermogravimetric analysis and differential scanning calorimetry were used to investigate the thermal decomposition character of the xerogel powder and the pattern of pure and doped BiFeO3 phases. Field emission scanning electron microscopy images show the surface crystallography of pure and Co-doped BiFeO3. Co-doped BiFeO3 has considerably reduced the crystallite and particle size of the samples. We have calculated the Eg of pure and doped BiFeO3 using a UV–Vis–NIR spectrophotometer and the results show the important reduction of Eg (1.60 eV) of the Co-doped samples, which may have potential applications in PV solar cells.
关键词： sol–gel,photovoltaic cells,Bandgap,nanoparticles,multiferroic
更新于2025-10-22 19:40:53
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An investigation of 60Co gamma radiation-induced effects on the properties of nanostructured α-MoO3 for the application in optoelectronic and photonic devices
摘要： Gamma ray has sufficient energy to ionize and displace of atoms when interacts with optoelectronic and photonic devices that are placed at γ-radiation exposure environment, can be exposed to gamma radiation, resulting the alteration of the physical properties and hence the performances of devices. A comprehensive investigation of physical properties of the semiconductor materials under the influence of gamma radiation is essential for the effective design of devices for the application in the radiation exposure environment. In this article, a potential candidate for optoelectronic and photonic devices, orthorhombic MoO3 nanoparticles with average crystallite size of 135.31 nm successfully synthesized by hydrothermal method. Then, the properties of nanoparticles exposed to low (10 kGy) and high (120 kGy) absorbed dose of γ-rays from 60Co source were characterized by XRD, FESEM, FTIR and UV–Vis–NIR spectrophotometer and effects of absorbed doses was investigated for the first time. A significant change is observed in different physical properties of α-MoO3 nanoparticles after gamma exposure. The XRD patterns reveal the average crystallite size, intensity and the degree of crystallinity decrease for low dose (10 kGy) and increases for high dose (120 kGy). The calculated average crystallite size exposed to low and high doses are 127.79 nm and 136 nm, respectively. The lattice strain and dislocation density, however, shows the opposite trend of crystallite size with absorbed doses. This result is good evidence for the deterioration of crystallinity for low dose and improvement for high dose. The FESEM results reveal the significant effects of gamma doses on the micrographs of layered structure and on grain size. The optical studies disclose that band gap increases gradually from 2.78 to 2.90 eV, this behavior is associated with the reduction of electronic localized states. These results suggest that α-MoO3 nanoparticles could tolerate high doses of gamma radiation, making it a promising candidate for optoelectronic and photonic devices for γ-ray exposure environment applications.
关键词： Optoelectronic and photonic devices,α-MoO3 nanoparticles,Co-60 gamma radiation,Optical bandgap,Structural properties
更新于2025-10-22 19:40:53
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Contactless parametric characterization of bandgap engineering in p-type FinFETs using spectral photon emission
摘要： In the last decade it has become increasingly popular to use germanium enriched silicon in modern field effect transistors (FET) due to the higher intrinsic mobility of both holes and electrons in SiGe as compared to Si. Whether used in the source/drain region (S/D) as compressive stressor, which is an efficient mobility booster on Si channel devices, or as channel material, the SiGe increases channel carrier mobility and thus enhancing device performance. Because the germanium content modifies the effective bandgap energy EG, this material characteristic is an important technology performance parameter. The bandgap energy can be determined in an LED-like operation of electronic devices, requiring forward biased p-n junctions. P-n junctions in FETs are source or drain to body diodes, usually grounded or reversely biased. This investigation applies a bias to the body that can trigger parasitic forward operation of the source/drain to body p-n junction in any FET. Spectral photon emission (SPE) is used here as a non-destructive method to characterize engineered bandgaps in operative transistor devices, while the device remains fully functional. Before applying the presented technique to a p-type FinFET device, it is put to the proof by verifying the nominal silicon bandgap on an (unstrained) 120 nm technology FET. Subsequently the characterization capability for bandgap engineering is then successfully demonstrated on a SiGe:C heterojunction bipolar transistor (HBT). In a final step, the bandgap energy EG of a 14/16 nm p-type FinFET was determined to be 0.84 eV, which corresponds to a Si0.7Ge0.3 mixture. The presented characterization technique is a contactless fault isolation method that allows for quantitative local investigation of engineered bandgaps in p-type FinFETs.
关键词： p-n junction,Heterojunction bipolar transistor,Bandgap characterization,p-channel FinFET,SiGe, strained Si,Body diode, parasitic operation,Bandgap engineering,Body bias voltage,HBT,Contactless fault isolation,Spectral photon emission,MOSFET
更新于2025-09-23 15:23:52
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Dense Electron-Hole Plasma Formation and Ultra-Long Charge Lifetime in Monolayer MoS <sub/>2</sub> via Material Tuning
摘要： Many-body interactions in photoexcited semiconductors can bring about strongly-interacting electronic states, culminating in the fully-ionized matter of electron-hole plasma (EHP) and electron-hole liquid (EHL). These exotic phases exhibit unique electronic properties, such as metallic conductivity and metastable high photoexcitation density, which can be the basis for future transformative applications. However, the cryogenic condition required for its formation has limited the study of dense plasma phases to a purely academic pursuit in a restricted parameter space. This paradigm can potentially change with the recent experimental observation of these phases in atomically thin MoS2 and MoTe2 at room temperature. A fundamental understanding of EHP and EHL dynamics is critical for developing novel applications on this versatile layered platform. In this work, we studied the formation and dissipation of EHP in monolayer MoS2. Unlike previous results in bulk semiconductors, our results reveal that electro-mechanical material changes in monolayer MoS2 during photoexcitation play a significant role in dense EHP formation. Within the free-standing geometry, photoexcitation is accompanied by an unconstrained thermal expansion, resulting in a direct-to-indirect gap electronic transition at a critical lattice spacing and fluence. This dramatic altering of the material’s energetic landscape extends carrier lifetimes by 2 orders of magnitude and allows the density required for EHP formation. The result is a stable dense plasma state that’s sustained with modest optical photoexcitation. Our findings pave the way for novel applications based on dense plasma states in 2D semiconductors.
关键词： 2D materials,Dense Electron-Hole Plasma,Bandgap Renormalization,MoS2,Transition Metal Dichalcogenides,Direct to Indirect Bandgap Transition
更新于2025-09-23 15:23:52