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Molecular Design Strategies for Efficient Intramolecular Singlet Exciton Fission
摘要： The process of carrier multiplication via singlet fission can potentially exceed Shockley–Queisser limit on the efficiency of single-junction photovoltaics. In the recent past, theoretical analysis provided the principal guidelines on molecular design strategies for singlet fission. In this perspective, we focus instead on correlating experimental results for different classes of reported singlet fission materials to identify principles to aid in the design of new molecules for efficient intramolecular singlet fission. Building on an evaluation of several series of multichromophoric and polymeric singlet fission materials, we extract new suggested strategies for molecular design.
关键词： singlet fission,photovoltaics,exciton multiplication,intramolecular singlet fission,molecular design
更新于2025-09-10 09:29:36
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Recent advances in bubble-assisted Liquid Hole-Multipliers in liquid xenon
摘要： We report on recent advances in the operation of bubble-assisted Liquid Hole-Multipliers (LHM). By con?ning a vapor bubble under or adjacent to a perforated electrode immersed in liquid xenon, we could record both radiation-induced ionization electrons and primary scintillation photons in the noble liquid. Four types of LHM electrodes were investigated: a THGEM, standard double-conical GEM, 50 μm-thick single-conical GEM (SC-GEM) and 125 μm-thick SC-GEM — all coated with CsI photocathodes. The 125 μm-thick SC-GEM provided the highest electroluminescence (EL) yields, up to ～ 400 photons per electron over 4π, with an RMS pulse-height resolution reaching 5.5% for events comprising ～ 7000 primary electrons. Applying a high transfer ?eld across the bubble, the EL yield was further increased by a factor of ～ 5. The feasibility of a vertical-mode LHM, with the bubble con?ned between two vertical electrodes, and the operation of a two-stage LHM con?guration were demonstrated for the ?rst time. We combine electrostatic simulations with observed signals to draw conclusions regarding the location of the liquid-gas interface and suggest an explanation for the observed di?erences in EL yield between the investigated electrodes.
关键词： Micropattern gaseous detectors (MSGC, GEM, THGEM, RETHGEM, MHSP, MICROPIC, MICROMEGAS, InGrid, etc),Noble liquid detectors (scintillation, ionization, double-phase),Charge transport, multiplication and electroluminescence in rare gases and liquids
更新于2025-09-09 09:28:46
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To the Problem of Optimization of Parameters of a Double Heterostructure Based on Direct-Gap Semiconductors for Avalanche Photodiodes
摘要： A double heterostructure based on direct-gap semiconductors with a photoabsorption middle layer at the avalanche breakdown voltage is considered. Such structures are used in the development of avalanche photodiodes with separate absorption and multiplication regions (APD with SAMR). It is shown that impact generation of electron–hole pairs should be considered in calculating the maximum possible characteristics of APDs with SAMR even in the absorption layer; therewith, this can be performed analytically.
关键词： avalanche photodiode,avalanche breakdown,multiplication,tunneling current,double heterostructure,doping,absorption
更新于2025-09-04 15:30:14
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Gaseous Radiation Detectors (Fundamentals and Applications) || Collisional excitations and charge multiplication in uniform fields
摘要： When the electric field is increased above a few kV/cm, more and more electrons can acquire enough energy between two collisions to produce inelastic phenomena, excitations of various kinds and ionizations. A molecule can have several characteristic modes of excitation, increasing in number and complexity for polyatomic molecules; typical values for the lowest excitation levels are between ten and twenty electron volts. In each collision, an electron can spend an amount of energy equal to or larger than the excitation energy; the atom or molecule, left in an excited state, returns to the ground state through single or multiple transitions.
关键词： breakdown,ionization,streamer formation,collisional excitations,inelastic electron–molecule collisions,charge multiplication,avalanche statistics
更新于2025-09-04 15:30:14
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An Ultra-Low-Jitter 22.8-GHz Ring-LC-Hybrid Injection-Locked Clock Multiplier With a Multiplication Factor of 114
摘要： An ultra-low-jitter, ring-LC-hybrid injection-locked clock multiplier (ILCM) is presented to achieve a high multiplication factor of 114. The proposed hybrid ILCM cascades a ring-type voltage-controlled oscillator (VCO)-based ILCM and an LC-type VCO-based ILCM. Using a dual-purpose frequency calibrator (DPFC) that can continuously calibrate the frequency drifts of the two VCOs, concurrently, the proposed ILCM can maintain excellent jitter performance against process-voltage-temperature (PVT) variations. Since the DPFC eliminates the use of an additional calibrator and operates at a very low frequency, it can reduce the expenditures for silicon and power. The proposed ILCM was fabricated in a 65-nm CMOS process. The RMS jitter of the 22.8-GHz output, integrated from 1 kHz to 100 MHz, was 153 fs, and the DPFC restricted its variations due to variations in temperatures and supply voltages to less than 180 fs. The proposed ILCM achieved the power efficiency of 0.32 mW/GHz. The active area was 0.2 mm2. The total power consumption was 7.4 mW, but the DPFC consumed only 400 μW.
关键词： ring-VCO,LC-voltage-controlled oscillator (VCO),clock multiplier,hybrid,multiplication factor,phase noise,jitter,Calibrator,injection locked
更新于2025-09-04 15:30:14