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Extent of Shallow/Deep Trap States beyond the Conduction Band Minimum in Defect-Tolerant CsPbBr <sub/>3</sub> Perovskite Quantum Dot: Control over the Degree of Charge Carrier Recombination
摘要： Perovskite quantum dots (PQDs) are known to be defect tolerant possessing clean band-gap with optically inactive benign defect states. However, we show that there exists significant deep trap states beyond conduction band minimum, although the extent of shallow trap states is observed to be minimal. Extent of deep trap states beyond conduction band minimum seem to significant in PQD, however the extent is less than even optically robust CdSe and InP based core/alloy-shell QDs. In-depth analyses based on ultrafast transient absorption and ultrasensitive single particle spectroscopic investigations decode the underlying degree of charge carrier recombination in CsPbBr3 PQD which are quite important for energy applications.
关键词： Perovskite quantum dots,ultrafast transient absorption,defect tolerant,single particle spectroscopy,charge carrier recombination,trap states
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE Pulsed Power & Plasma Science (PPPS) - Orlando, FL, USA (2019.6.23-2019.6.29)] 2019 IEEE Pulsed Power & Plasma Science (PPPS) - 2D Simulations of the NS-Laser Shock Peening
摘要： We report on the impact of H2 high-pressure annealing (HPA) onto In0.7Ga0.3As MOSCAPs and quantum-well (QW) MOSFETs with Al2O3/HfO2 gate-stack. After HPA with process condition of 300 °C, H2 ambient and pressure of 20 atm, we observed notable improvements of the capacitance–voltage (CV) characteristics in InGaAs MOSCAPs with Al2O3/HfO2 gate-stack, such as reduction of equivalent-oxide-thickness and less frequency dispersion in the accumulation region. There was 20% improvement of the interfacial trap density ( Dit). Then, we incorporated the HPA process into the fabrication of sub-100-nm In0.7Ga0.3As QW MOSFETs, to investigate the impact of HPA process. After HPA process, the device with L g = 50 nm exhibits improved subthreshold-swing (SS) = 105 mV/decade, in comparison with SS = 130 mV/decade for the reference device without HPA process. Finally, we carried out reliability assessment under a constant-voltage-stress (CVS), and it turns out that the HPA process was effective in mitigating a shift of threshold voltage ((cid:2)VT ) during the CVS. These are attributed to the effective passivation of oxide traps in the high-k dielectric layer and interfacial traps, after HPA process in the H2 ambient.
关键词： interfacial trap density (Dit),subthreshold-swing (SS),high-pressure annealing,atomic layer deposition (ALD),InGaAs MOSFET
更新于2025-09-19 17:13:59
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Investigation of Oxygen Passivation for High-Performance All-Inorganic Perovskite Solar Cells
摘要： Defect passivation using oxygen has been identified as an efficient and convenient approach to suppress non-radiative recombination and improve the photovoltaic performance of hybrid organic-inorganic halide perovskites (HHPs). However, oxygen can seriously undermine the chemical stability of HHPs due to the reaction of superoxide with protonated organic cations such as CH3NH3+ and [(NH2)2CH]+, thus hindering the deep understanding of how oxygen affects their defect properties. Here we substitute free-proton inorganic Cs+ for organic moiety to avoid the negative effect of oxygen and then systematically investigate the oxygen passivation mechanism in all-inorganic halide perovskites (IHPs) from theory to experiment. We find that, in contrast to conventional oxygen molecule passivation just through physisorption on the surface of perovskites, oxygen atom can provide better passivation effect due to its stronger interaction with perovskites. The key point to achieve O-passivated perovskites rather than O2 is the dry-air processing condition, which can dissociate the O2 into O during the annealing process. O-passivated IHP solar cells exhibit enhanced power conversion efficiency (PCE) and better air stability than O2-passivated cells. These results not only provide deep insights into the passivation effect of oxygen on perovskites, but also demonstrate the great potential of IHPs for high photovoltaic performance with simplified ambient processing.
关键词： oxygen passivation,perovskite solar cells,CsPbI2Br,trap states,photovoltaics
更新于2025-09-19 17:13:59
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Selfa??Crystallized Multifunctional 2D Perovskite for Efficient and Stable Perovskite Solar Cells
摘要： Recently, perovskite solar cells (PSC) with high power-conversion efficiency (PCE) and long-term stability have been achieved by employing 2D perovskite layers on 3D perovskite light absorbers. However, in-depth studies on the material and the interface between the two perovskite layers are still required to understand the role of the 2D perovskite in PSCs. Self-crystallization of 2D perovskite is successfully induced by deposition of benzyl ammonium iodide (BnAI) on top of a 3D perovskite light absorber. The self-crystallized 2D perovskite can perform a multifunctional role in facilitating hole transfer, owing to its random crystalline orientation and passivating traps in the 3D perovskite. The use of the multifunctional 2D perovskite (M2P) leads to improvement in PCE and long-term stability of PSCs both with and without organic hole transporting material (HTM), 2,2′,7,7′-tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,9′-spirobifluorene (spiro-OMeTAD) compared to the devices without the M2P.
关键词： trap passivation,hole-transporting layers,hole-transfer facilitators,2D perovskites,perovskite solar cells
更新于2025-09-19 17:13:59
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Charge Transport and Photovoltaic Properties of Conjugated Polymer PTB7:PC71BM Based Solar Cells
摘要： We investigate the charge transport in organic solar cells based on PTB7:PC71BM by measuring the J (V) characteristics at different temperatures (140–325 K). In dark, two models dominate the transport. The Ohmic law overcomes for the low applied low voltages, and for high voltages the trapped charge limited current governs the transport with an average total concentration of trap around 5.62 × 1015 cm?3. At higher voltages there is evidence of an electrode-to-bulk limited transition, with conductivity dominated by the Poole–Frenkel effect. The photovoltaic conversion properties of the junction were also studied by carrying out the J–V measurements at room temperature under illumination of 100 mW/cm2 and a power conversion efficiency of 6.49% has been achieved. the other cell parameters, the short-circuit current density JSC, the open circuit voltage VOC and de fill factor FF, were found to be 12.87 mA/cm2, 0.77 V and 0.65 respectively. These values were compared with other organic solar cells found in literature.
关键词： Charge transport,Photovoltaics,Organic materials,Trap density
更新于2025-09-19 17:13:59
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Solvent engineering of LiTFSI towards high-efficiency planar perovskite solar cells
摘要： The performance and stability of perovskite solar cell (PSC) are inseparable from the quality of perovskite film, and the solvent engineering is being seemed as an effective strategy to enhance the properties of perovskite. Acetonitrile (ACN) is often used as a solvent to dissolve bis(trifluoromethane)sulfonimide lithium salt (LiTFSI), but ACN can corrode the perovskite film, which hinders the promotion of PSC efficiency and durability. Herein, a solvent engineering approach is implemented to search for suitable alternatives for ACN to abate the degradation of the perovskite films. The results demonstrate that isopropanol (IPA) with smaller polarity can effectively dissolve LiTFSI and slow down the degradation of the perovskite layer compared with ACN, which can result in the reduction of defects as well as the nonradiative recombination. Consequently, the devices using LiTFSI/IPA as additive achieve superior power conversion efficiencies (PCEs) with relatively less hysteresis effects and get a champion PCE of 19.43%, while the device using LiTFSI/ACN gets an inferior PCE of 17.12%.
关键词： Trap density,Nonradiative recombination,Solvent engineering,Isopropanol,Perovskite solar cells
更新于2025-09-16 10:30:52
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[IEEE 2019 International Conference on Communication and Electronics Systems (ICCES) - Coimbatore, India (2019.7.17-2019.7.19)] 2019 International Conference on Communication and Electronics Systems (ICCES) - Standalone PV System Integrated with Hysteresis Current Controlled Inverter using MPPT Techniques
摘要： Harmonic stability problems caused by the resonance of high-order ?lters in power electronic systems are ever increasing. The use of passive damping does provide a robust solution to address these issues, but at the price of reduced ef?ciency due to the presence of additional passive components. Hence, a new method is proposed in this paper to optimally design the passive damping circuit for the LCL ?lters and LCL with multituned LC traps. In short, the optimization problem reduces to the proper choice of the multisplit capacitors or inductors in the high-order ?lter. Compared to existing design procedures, the proposed method simpli?es the iterative design of the overall ?lter while ensuring the minimum resonance peak with a lower damping capacitor and a lower rated resistor. It is shown that there is only one optimal value of the damping resistor or quality factor to achieve a minimum ?lter resonance. The passive ?lters are designed, built, and validated both analytically and experimentally for veri?cation.
关键词： Harmonic passive ?lters,LCL ?lter,resonance damping,voltage-source converters,trap ?lter
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Plug-and-Play Generation and Manipulation of Squeezing on Chip
摘要： We propose a novel graphic method to enable the analysis of the field-effect transistor (FET) threshold voltage variation (cid:2)Vth due to random telegraph signals in a percolative channel. First, through technology computer-aided design simulation with no percolation, both a minimum (cid:2)Vth and a critical curve in a mloc ? σloc plot are produced. The former constitutes a statistical distribution far away from the conventional log-normal one. In the latter, mloc and σloc are the mean and the standard deviation, respectively, of a well-known normal variable in Mueller–Schulz’s percolation theory. The critical mloc ? σloc curve divides the plot into the allowed region and the forbidden region and will go down with increasing gate size. Then, (cid:2)Vth contours in the allowed region are graphically created. While applying to existing experimental (cid:2)Vth statistical distributions of SiON- and high-k metal gate (HKMG)-scaled FETs, resulting paired mloc and σloc at high (cid:2)Vth remain intact, regardless of gate size or gate stack type. This means that the underlying percolation patterns resemble each other, due to the same manufacturing process used. However, if these paired mloc and σloc fall in the forbidden region, it is the critical mloc ? σloc curve dominating. Application to bias and temperature instability statistical data in literature is straightforwardly well done.
关键词： percolation,technology computer-aided design (TCAD),Bias and temperature instability (BTI),trap,random telegraph signals (RTSs),field-effect transistors (FETs)
更新于2025-09-16 10:30:52
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Trap States, Electric Fields, and Phase Segregation in Mixeda??Halide Perovskite Photovoltaic Devices
摘要： Mixed-halide perovskites are essential for use in all-perovskite or perovskite–silicon tandem solar cells due to their tunable bandgap. However, trap states and halide segregation currently present the two main challenges for efficient mixed-halide perovskite technologies. Here photoluminescence techniques are used to study trap states and halide segregation in full mixed-halide perovskite photovoltaic devices. This work identifies three distinct defect species in the perovskite material: a charged, mobile defect that traps charge-carriers in the perovskite, a charge-neutral defect that induces halide segregation, and a charged, mobile defect that screens the perovskite from external electric fields. These three defects are proposed to be MA+ interstitials, crystal distortions, and halide vacancies and/or interstitials, respectively. Finally, external quantum efficiency measurements show that photoexcited charge-carriers can be extracted from the iodide-rich low-bandgap regions of the phase-segregated perovskite formed under illumination, suggesting the existence of charge-carrier percolation pathways through grain boundaries where phase-segregation may occur.
关键词： halide segregation,perovskites,electric fields,trap states,photovoltaic devices
更新于2025-09-16 10:30:52
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[IEEE 2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama) - Toyama (2018.8.1-2018.8.4)] 2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama) - A Chip of Pulse-Laser-Assisted Dual-Beam Fiber-Optic Trap
摘要： Compared with the single-beam gradient optical trap, the dual-beam optical trap based on micro-structure eliminates the need for complex optical alignment and offers intrinsic benefits of miniaturization and stabilization, which are crucial for developing a practical sensor. We design a monolithic chip of dual-beam fiber-optic trap which allows extremely accurate alignment of submicron scale between two counter-propagating fiber beams. Based on micromachining technology, the chip featured a V-shaped groove to align the fibers and a rectangular channel to load the particles is experimentally realized. Recent studies have demonstrated that micro-scale particles can be removed effectively from substrate by focused pulse laser beam. To acquire high trapping efficiency and better trapping stability, we propose a new loading method that combinates pulse laser with dual-beam fiber-optic trap. We have fabricated a silica miniature operating rod for initial storage of the microspheres and moved a targeted particle into the effective trapping area of the fiber-optic trap. Optical loading and trapping of a 10 μm polystyrene particle in air are demonstrated and the controllable capturing process avoids any contamination on fiber ends, which ensures the reliability of optical path. We use a microscopic imaging system and image processing method to test the static stability of the captured particle. The static stability of the microspheres is submicron, which is clearly superior to the test results in liquid environment. The rapid loading and manipulation of microspheres in optical trap is significant for its applications in optomechanics and precision force sensing. Our results pave the way for a new class of monolithic and portable optical sensor for inertial measurement.
关键词： micromachining,fiber-optic trap,optical sensor,dual-beam optical trap,pulse laser
更新于2025-09-12 10:27:22