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Highly luminescent and stable CH3NH3PbBr3 quantum dots with 91.7% photoluminescence quantum yield: Role of guanidinium bromide dopants
摘要： Although perovskite quantum dots (PQDs) have received considerable attention, defects in PQDs can significantly degrade the properties and device performance. In this study, we report on an effective strategy for synthesizing highly luminescent CH3NH3PbBr3 quantum dots (QDs) by a simple doping. To remove such defects, guanidinium bromide (GuBr) was doped into the CH3NH3PbBr3 QDs synthesized by the ligand-assisted reprecipitation technique. From XRD and TEM studies, the doping of GuBr into the QD lattices was verified. In addition, the surfaces of PQDs with and without GuBr dopants were analyzed by XPS to trace the metallic Pb acting as a major recombination center. The GuBr doping resulted in the size uniformity of QDs and effectively eliminated defects and metallic Pb, which enhanced the photoluminescence quantum yield (PLQY) through the inhibition of the non-radiative recombination pathway. Furthermore, the recombination dynamics in the QDs were examined by using time-resolved photoluminescence and fluorescence lifetime imaging to verify the role of GuBr dopants. By optimizing the amount of GuBr doping, the CH3NH3PbBr3 QDs with strong green emission achieved a maximum PLQY of 91.7%.
关键词： Photoluminescence quantum yield,Fluorescence lifetime imaging,CH3NH3PbBr3 quantum dots,Guanidinium bromide,Recombination centers
更新于2025-09-23 15:19:57
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Physicala??Chemical Properties of Self-Assembled Structures in Solution of Zinc Phthalocyanine and Bis-3-pentyl-PTCDI Derivative
摘要： For the first time, in this work, we succeed in synthesizing in solution a novel supramolecular self-assembled zinc phthalocyanine (ZnPc) and N,N′-bis(3-pentyl)-perylene-3,4,9,10-bis(dicarboximide) (bis-3-pentyl-PTCDI) system with improved light absorption and phosphorescence lifetime of the charge separated states up to 2.5 ms. Moreover, the structural and optical properties of undoped and doped with iodine ZnPc thin films were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman analysis, and UV?vis spectroscopy. Analysis of ZnPc:I2:bis-3-pentyl-PTCDI blend in a 2:1 ratio shows that sandwich complexes between them result in improved bulk properties as compared to those of the single-component systems.
关键词： light absorption,Fourier transform infrared spectroscopy,UV?vis spectroscopy,bis-3-pentyl-PTCDI,X-ray diffraction,supramolecular self-assembly,X-ray photoelectron spectroscopy,zinc phthalocyanine,phosphorescence lifetime,Raman analysis
更新于2025-09-23 15:19:57
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Novel Positive Polaron Stabilizing n-Type Host for High Efficiency and Long Lifetime in Blue Phosphorescent Organic Light-Emitting Diodes
摘要： Four electron transport type hosts withstanding the positive polaron stress were synthesized using the benzo[4,5]thieno[3,2-d]pyrimidine core to develop high triplet energy hosts. Four benzo[4,5]thieno[3,2-d]pyrimidine-derived hosts, 4-(9H-carbazol-9-yl)-2-(3-(triphenylsilyl)phenyl)benzo[4,5]thieno[3,2-d]pyrimidine (CzBTPmSi), 2,4-di(9H-carbazol-9-yl)benzo[4,5]thieno[3,2-d]pyrimidine (2CzBTP), 2-(9H-carbazol-9-yl)-4-(3-(triphenylsilyl)phenyl)benzo[4,5]thieno[3,2-d]pyrimidine (mSiBTPCz), and 2,4-bis(3-(triphenylsilyl)phenyl)benzo[4,5]thieno-[3,2-d]pyrimidine (2mSiBTP), were designed to have either the tetraphenylsilyl blocking group or the hole transport type carbazole group. The CzBTPmSi and mSiBTPCz were prepared to study the effect of substitution positions of tetraphenylsilyl and carbazole on the device performances, and the 2CzBTP and 2mSiBTP were synthesized as reference materials. In the device application, the four hosts were used as electron transport type hosts mixed with a hole transport type 3,3′-di(9H-carbazol-9-yl)-1,1′-biphenyl (mCBP) host in the mixed host. Among the four mixed hosts, the mCBP/CzBTPmSi mixed host showed an external quantum efficiency of 23.9% and a device lifetime over 4000 h at 100 cd m?2 in the blue phosphorescent organic light-emitting diodes.
关键词： host,electron transport,efficiency,benzothienopyrimidine,lifetime
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - On the Origin of Silicon Lifetime Degradation During Anneal in III-V Material Growth Chambers
摘要： Silicon bulk lifetime degradation in III-V material growth chambers has been a major hindrance to the development of III-V/Si tandem solar cells. While the exact mechanisms responsible for this degradation remain unknown, many researchers have attributed such degradation to extrinsic contaminants that diffuse into silicon bulk during growth. In this work, we show that thermal activation of grown-in defects in ?oat zone wafers is also a key mechanism behind such degradation. Annealing of the wafer at 1000 ?C to remove these defects, together with a SiNX diffuse barrier layer deposition are both required to preserve the silicon bulk lifetime.
关键词： grown-in defects,diffuse barrier,III-V/Si,silicon bulk lifetime degradation
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Performance of silicon heterojunction solar cells using high resistivity substrates
摘要： We investigate the potential advantages of using very high resistivity n- and p-type, to manufacture high performance solar cells. Analytical modeling indicates that high resistivity substrates (10 Ωcm - >1k Ωcm) are required to have bulk Shockley-Read-Hall lifetimes in the millisecond range to outperform wafers with standard resistivities (< 10 Ωcm). Additionally, for resistivities over 10 Ω.cm, efficiencies show to be weakly dependent of the bulk resistivity. These results if experimental verified, can lead to more affordable manufacturing, by lessening the requirements of dopants homogeneity along the ingot. We successfully passivated both n- and p- type substrates using i-a-Si:H, obtaining surface saturation current densities below 10 fAcm-2 and effective minority-carrier lifetimes over 2 ms at maximum power over the entire range of bulk resistivities (3 Ωcm- >10k Ωcm).
关键词： photovoltaic cells,doping,charge carrier lifetime,silicon,amorphous materials
更新于2025-09-23 15:19:57
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Ultra-long carrier lifetime in neutral graphene-hBN van der Waals heterostructures under mid-infrared illumination
摘要： Graphene/hBN heterostructures are promising active materials for devices in the THz domain, such as emitters and photodetectors based on interband transitions. Their performance requires long carrier lifetimes. However, carrier recombination processes in graphene possess sub-picosecond characteristic times for large non-equilibrium carrier densities at high energy. An additional channel has been recently demonstrated in graphene/hBN heterostructures by emission of hBN hyperbolic phonon polaritons (HPhP) with picosecond decay time. Here, we report on carrier lifetimes in graphene/hBN Zener-Klein transistors of ~30 ps for photoexcited carriers at low density and energy, using mid-infrared photoconductivity measurements. We further demonstrate the switching of carrier lifetime from ~30 ps (attributed to interband Auger) down to a few picoseconds upon ignition of HPhP relaxation at finite bias and/or with infrared excitation power. Our study opens interesting perspectives to exploit graphene/hBN heterostructures for THz lasing and highly sensitive THz photodetection as well as for phonon polariton optics.
关键词： photodetectors,mid-infrared,phonon polaritons,van der Waals heterostructures,THz,Graphene,carrier lifetime,hBN
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Singapore, Singapore (2019.8.28-2019.8.30)] 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Near Infrared Absorption Enhancement of Graphene for High-Responsivity Photodetection
摘要： As a key component in the wind turbine system, the power electronic converter and its power semiconductors suffer from complicated power loadings related to environment, and are proven to have high failure rates. Therefore, correct lifetime estimation of wind power converter is crucial for the reliability improvement and also for cost reduction of wind power technology. Unfortunately, the existing lifetime estimation methods for the power electronic converter are not yet suitable in the wind power application, because the comprehensive mission profiles are not well specified and included. Consequently, a relative more advanced approach is proposed in this paper, which is based on the loading and strength analysis of devices and takes into account different time constants of the thermal behaviors in power converter. With the established methods for loading and lifetime estimation for power devices, more detailed information of the lifetime-related performance in wind power converter can be obtained. Some experimental results are also included to validate the thermal behavior of power device under different mission profiles.
关键词： lifetime prediction,IGBT,power semiconductor device,thermal cycling,wind power,mission profiles
更新于2025-09-23 15:19:57
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11,11-Dimethyl-11H-indeno[1,2-b]indolo[1,2,3-jk]carbazole: A rigid chromophore with novel amalgamation strategy for long lifetime blue fluorescent organic light-emitting diodes
摘要： In this work, we report a novel chromophore, 11,11-dimethyl-11H-indeno[1,2-b]indolo[1,2,3-jk]carbazole (IDFL), developed from a indenocarbazole building block and a blue fluorescent emitter, 11,11-dimethyl-N2,N2,N8,N8-tetraphenyl-11H-indeno[1,2-b]indolo[1,2,3-lm]carbazole-2,8-diamine (IDFL-2DPA), derived from the IDFL by diphenylamine functionalization. The device fabricated using the IDFL-2DPA emitter offered blue emission with a very small full-width at half maximum of 32 nm in addition to high external quantum efficiency above 5% and 4 times longer lifetime than that of pyrene-based blue device. Therefore, the IDFL-2DPA emitter was appropriate as the pure blue emitter with high color purity, high efficiency, and long device lifetime.
关键词： blue fluorescent emitters,lifetime,Chromophore,TTA
更新于2025-09-23 15:19:57
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Long carrier lifetime in faceted PbS quantum dot superlattice fabricated by sedimentation method
摘要： We fabricated colloidal quantum dot (QD) superlattice films and investigated their primal optical properties. The films were prepared by depositing faceted PbS QDs on pyramidal-microhole-array template and flat substrate in solution. The red shift in the quantum state emission of QDs was observed in photoluminescence spectra after film formation, which suggested the weakened quantum confinement of carriers in intermediate bands. Emission decay curves at the excited states in the QD superlattice film were double exponential. The longer lifetime was several tens of nanoseconds and attributed to the carrier delocalization in the intermediate bands. The emission lifetime of the QD film prepared on the template was found to be more than twice as long as that on the flat substrate, which suggested that the template helped to form large area QD superlattice.
关键词： sedimentation method,colloidal quantum dot,PbS,superlattice,carrier lifetime
更新于2025-09-23 15:19:57
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Electron and proton irradiation effect on the minority carrier lifetime in SiC passivated p-doped Ge wafers for space photovoltaics
摘要： We report on the effect of electron and proton irradiation on effective minority carrier lifetimes (τeff) in p-type Ge wafers. Minority carrier lifetimes are assessed using the microwave-detected photoconductance decay (μW-PCD) method. We examine the dependence of τeff on the p-type doping level and on electron and proton radiation fluences at 1 MeV. The measured τeff before and after irradiation are used to estimate the minority carriers’ diffusion lengths, which is an important parameter for solar cell operation. We observe τeff ranging from ~50 to 230 μs for Ge doping levels between 1 × 1017 and 1 × 1016 at.cm-3, corresponding to diffusion lengths of ~500–1400 μm. A separation of τeff in Ge bulk lifetime and surface recombination velocity is conducted by irradiating Ge lifetime samples of different thicknesses. The possible radiation-induced defects are discussed on the basis of literature.
关键词： Space photovoltaics,Minority carrier lifetime,Germanium,Surface passivation,Irradiation
更新于2025-09-23 15:19:57