Charge Yield Research Articles

Facet-Engineered BiVO4 Photocatalysts for Water Oxidation: Lifetime Gain Versus Energetic Loss.

A limiting factor to the efficiency of water Oxygen Evolution Reaction (OER) in metal oxide nanoparticle photocatalysts is the rapid recombination of holes and electrons. Facet-engineering can effectively improve charge separation and, consequently, OER efficiency. However, the kinetics behind this improvement remain poorly understood. This study utilizes photoinduced absorption spectroscopy to investigate the charge yield and kinetics in facet-engineered BiVO4 (F-BiVO4) compared to a non-faceted sample (NF-BiVO4) under operando conditions. A significant influence of preillumination on hole accumulation is observed, linked to the saturation and, thus, passivation of deep and inactive hole traps on the BiVO4 surface. In DI-water, F-BiVO4 shows a 10-fold increase in charge accumulation (∼5 mΔOD) compared to NF-BiVO4 (∼0.5 mΔOD), indicating improved charge separation and stabilization. With the addition of Fe(NO3)3, an efficient electron acceptor, F-BiVO4 demonstrates a 30-fold increase in the accumulation of long-lived holes (∼45 mΔOD), compared to NF-BiVO4 (∼1.5 mΔOD) and an increased half-time, from 2 to 10 s. Based on a simple kinetic model, this increase in hole accumulation suggests that facet-engineering causes at least a 50-100 meV increase in band bending in BiVO4 particles, thereby stabilizing surface holes. This energetic stabilization/loss results in a retardation of OER relative to NF-BiVO4. This slower catalysis is, however, offset by the observed increase in density and lifetime of photoaccumulated holes. Overall, this work quantifies how surface faceting can impact the kinetics of long-lived charge accumulation on metal oxide photocatalysts, highlighting the trade-off between lifetime gain and energetic loss critical to optimizing photocatalytic efficiency.

60Co gamma radiation effects on NPN transistor at cryogenic temperature.

The 60Co gamma radiation effects on the DC electrical characteristics of silicon NPN transistor were studied in the dose range of 100krad to 6Mrad at room temperature (300K) and cryogenic temperature (77K). The measurements were carried out at both 300 and 77K temperature. The electrical characteristics such as Gummel characteristics, excess base current (ΔIB), current gain (hFE), transconductance (gm) and output characteristics were studied in situ as a function of total dose. The results show that there is a considerable degradation in the electrical parameters of the device irradiated both at 300 and 77K as a consequence of increase in excess base current (ΔIB) because of the formation of generation and recombination centers in the emitter-base spacer oxide (SiO2). At cryogenic temperature irradiation, the degradation in electrical characteristics is less because of the physical phenomena such as carrier freezeout effect, decreased recombination rate, reduced charge yield, decreased electron mobility, etc.

Design and performance of the field cage for the XENONnT experiment

The precision in reconstructing events detected in a dual-phase time projection chamber depends on an homogeneous and well understood electric field within the liquid target. In the XENONnT TPC the field homogeneity is achieved through a double-array field cage, consisting of two nested arrays of field shaping rings connected by an easily accessible resistor chain. Rather than being connected to the gate electrode, the topmost field shaping ring is independently biased, adding a degree of freedom to tune the electric field during operation. Two-dimensional finite element simulations were used to optimize the field cage, as well as its operation. Simulation results were compared to 83mKr\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${}^{83\ extrm{m}}\\hbox {Kr }$$\\end{document}calibration data. This comparison indicates an accumulation of charge on the panels of the TPC which is constant over time, as no evolution of the reconstructed position distribution of events is observed. The simulated electric field was then used to correct the charge signal for the field dependence of the charge yield. This correction resolves the inconsistent measurement of the drift electron lifetime when using different calibrations sources and different field cage tuning voltages.

Missing Excitons: How Energy Transfer Competes with Free Charge Generation in Dilute-Donor/Acceptor Systems.

Energy transfer across the donor-acceptor interface in organic photovoltaics is usually beneficial to device performance, as it assists energy transport to the site of free charge generation. Here, we present a case where the opposite is true: dilute donor molecules in an acceptor host matrix exhibit ultrafast excitation energy transfer (EET) to the host, which suppresses the free charge yield. We observe an optimal photochemical driving force for free charge generation, as detected via time-resolved microwave conductivity (TRMC), but with a low yield when the sensitizer is excited. Meanwhile, transient absorption shows that transferred excitons efficiently produce charge-transfer states. This behavior is well described by a competition for the excited state between long-range electron transfer that produces free charge and EET that ultimately produces only localized charge-transfer states. It cannot be explained if the most localized CT states are the intermediate between excitons and the free charge in this system.

Characterization of Cl-doped two-dimensional (PEA)2PbBr4 perovskite single crystals for fast neutron and gamma ray detection.

In this paper, a high-quality Cl-doped two-dimensional halide perovskite (PEA)2Pb(Br0.95Cl0.05)4 crystal was prepared using a seed-induced volatile solvent method. On optimizing the Cl- doping concentration, we found that 5% Cl-doping results in (PEA)2PbBr4 with the highest optical and photon yield. Based on the Cl-doped (PEA)2PbBr4 single crystal, the response characterization of the (PEA)2Pb(Br0.95Cl0.05)4 crystal in the mixed field of neutrons and gamma rays (n/γ) has been verified. Using the time-of-flight method and the linear relationship between integral charge and neutron yield, it was proved that (PEA)2Pb(Br0.95Cl0.05)4 crystal can be used for n/γ screening. The time difference between the fast neutron released by a single nuclear reaction and the γ photon arriving at the detector was 130 ns, and the arrival time of the γ photon is earlier than that of the fast neutron. This work has a broad application prospect in the study of nuclear reaction kinetics, the monitoring of the neutron yield of fusion devices and the total energy released by nuclear reactions.

The effect of infrared push pulse on the relaxed exciton in single-component organic solar cells

Ultrafast pump-push-probe/photocurrent experiments have confirmed that free charges can be spontaneously generated in single-component organic solar cells. A deeper understanding of the experimental results is expected to further modulate the charge yield. Herein, the effect of an infrared push pulse on the relaxed exciton in conjugated polymers is theoretically studied. We find that the relaxed exciton can be pushed into different hot excitons depending on the energy of this infrared pulse. In particular, the dynamics of the transition from localized to delocalized excitons is explicitly presented. Moreover, we attempt to demonstrate that the delocalization effect of hot exciton is favorable for charge generation by introducing a driving field. The results suggest that the strength of the driving field and timescale required for the dissociation of hot exciton is significantly reduced compared to this relaxed exciton. Finally, the influence of the photoexcitation conditions on the charge generation is discussed to further elucidate the effect of hot exciton delocalization. Overall, this work has the potential to provide further information for the analysis and control of charge generation by hot exciton dissociation.

Damage Separation in Proton-Irradiated Bipolar Junction Transistors as a Function of Energy

Damage separation analysis was performed for two types of bipolar junction transistors following proton irradiation over the energy range of 1.6 to 650 MeV. The functional dependence of excess base current on fluence for each device type is consistent with base polarity as it relates to the effect of oxide-trapped charge on surface recombination. For a given fluence, the excess base current decreases with proton energy due to reductions in NIEL and stopping power. Relative damage coefficients, computed from normalized Δ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</sub> vs fluence curves, imply a mix of ionization and displacement damage. The relative amounts of ionization damage and displacement damage as a function of proton energy are consistent with charge yield, stopping power and NIEL. A simple model for the energy dependence of damage contributions, based on charge yield and the relative amounts of deposited ionizing and non-ionizing energy, is described. The model calculations as a function of proton energy are in good agreement with the relative damage contributions estimated from the damage separation analysis.

Investigation and Band Gap Analysis of Pulsed Dc Magnetron Sputtered Diamond‐Like Carbon to Enhance Contact‐Electrification and Durability of Triboelectric Nanogenerators

AbstractThis work details the triboelectric characteristics of diamond‐like carbon (DLC) film where a proportioned sp3:sp2 bond ratio is engineered through a patented pulsed DC magnetron sputtering process to achieve a durable commercial energy harvesting material. A triboelectric nanogenerator (TENG) is fabricated by creating the triboelectric interface between DLC and PTFE. The presence and synchronization of σ – σ and σ – π bonds between DLC‐PFTE contact surface amplify the electronic cloud overlap between their atoms leading to an enhancement of the triboelectric surface charge density. The inherent hardness and reduced friction achieved through DLC and PTFE respectively prevent the mass transfer, and consequent power loss upon consecutive mechanical contact and achieves a stable electric power output of 141 mW m−2. The DLC durability achieved with PTFE in TENG demonstrates its significant potential as low frequency (1 – 10 Hz) energy harvesting devices and self‐/low‐power electronic devices and sensors. The paper uniquely contributes to a better understanding of the triboelectrification mechanism by insightfully detailing the band‐to‐band transition of electrons between the PTFE and DLC tribo‐interface, as well as discussing gap and frequency limitation of the tribo‐pair on the triboelectric charge yield, storage, transfer, and on the friction layer electric field.

Observation of time-dependent internal charge amplification in a planar germanium detector at cryogenic temperature

For the first time, time-dependent internal charge amplification through impact ionization has been observed in a planar germanium (Ge) detector operated at cryogenic temperature. In a time period of 30 and 45 min after applying a bias voltage, the charge energy corresponding to a baseline of the 59.54 keV gamma rays from a ^{241}Am source is amplified for a short period of time and then decreases back to the baseline. The amplification of charge energy depends strongly on the applied positive bias voltage with drifting holes across the detector. No such phenomenon is visible with drifting electrons across the detector. We find that the observed charge amplification is dictated by the impact ionization of charged states, which has a strong correlation with impurity level and applied electric field. We analyze the dominant physics mechanisms that are responsible for the creation and the impact ionization of charged states. Our analysis suggests that the appropriate level of impurity in a Ge detector can enhance charge yield through the impact ionization of charged states to achieve extremely low-energy detection threshold (< 10 meV) for MeV-scale dark matter searches if the charge amplification can be stabilized.

Lindhard integral equation with binding energy applied to light and charge yields of nuclear recoils in noble liquid detectors

We present a model of the ionization efficiency, or quenching factor, for low-energy nuclear recoils, based on a solution to Lindhard integral equation with binding energy and apply it to the calculation of the relative scintillation efficiency and charge yield for nuclear recoils in noble liquid detectors. The quenching model incorporates a constant average binding energy together with an electronic stopping power proportional to the ion velocity, and is an essential input in an analysis of charge recombination processes to predict the ionization and scintillation yields. Our results are comparable to NEST simulations of LXe and LAr and are in good agreement with available data. These studies are relevant to current and future experiments using noble liquids as targets for neutrino physics and the direct searches for dark matter.

Boosting photoelectron transport in Zn0.5Cd0.5S/Sn3O4 heterostructure through close interface contact for enhancing photocatalytic H2 generation and degradation of tetracycline hydrochloride

Reasonable design and construction of heterogeneous photocatalysts with close interface contact are considered as the effective strategy to realize the application of highly efficient solar for hydrogen evolution and pollutant degradation. Here, a novel Zn0.5Cd0.5S nanospheres/Sn3O4 nanosheets (ZCS/SO) heterostructure photocatalyst was firstly synthesized using a simple hydrothermal method, where Zn0.5Cd0.5S nanospheres in-situ grew on the surfaces of Sn3O4 nanosheets derived by ultrasonicating Sn3O4 nanoflowers. The synthesized ZCS/SO heterostructure exhibited much higher photocatalytic activity for H2 production and tetracycline hydrochloride (TCH) degradation than pristine Sn3O4 and Zn0.5Cd0.5S. The optimal ZCS/SO-10 performed the highest rate of hydrogen production of 7.19 mmol·g−1·h−1, which was 112.3 and 3.6 times those of Sn3O4 and Zn0.5Cd0.5S, respectively. And the AQY of ZCS/SO-10 for H2 evolution was up to 16.6 % at λ = 420 nm. Moreover, ZCS/SO-10 displayed the highest TCH degradation rate (0.0484 min−1), which were 228.3 and 1.9 times those of Sn3O4 (0.000212 min−1) and Zn0.5Cd0.5S (0.0249 min−1). Such excellent dual-functional photocatalytic performance of ZCS/SO heterostructure could be attributed to the synergistic effect between Sn3O4 and Zn0.5Cd0.5S as well as the formation of heterogenous interfaces with close contacts, which greatly increased specific surface area, enlarged spectral response range, enhanced hydrophilicity and accelerated photogenerated charge transfer, resulting in the improvement of photogenerated charge yield and photoreaction efficiency. Detailed electron transport mechanisms and possible degradation paths of TCH were also proposed. This work provides a feasible strategy for the preparation of transition metal sulfide photocatalysts efficiently utilizing solar energy to realize the production of clean energy and water environmental remediation.

Dopant-induced modulation of lithium-ion conductivity in cubic garnet solid electrolytes: a first-principles study.

Cubic garnet Li7La3Zr2O12 (c-LLZO) is a promising solid electrolyte for all-solid-state batteries, often doped with Ga, Al, and Fe to stabilize the structure and enhance Li-ion conductivity. Despite introducing the same amount of Li vacancies, these dopants with +3 classical charge yield different Li-ion conductivities by around an order of magnitude. In this study, we used density functional theory (DFT) calculations to investigate the impact of Ga, Fe, and Al dopants on Li chemical potential and Li-ion conductivity variations. We identified the energetically favorable dopant location in c-LLZO and determined the optimal U value of 7.5 eV for DFT+U calculations for dopant Fe in c-LLZO. Our calculations showed that Ga or Fe doping enhances the Li chemical potential by 0.05-0.08 eV, reducing Li-ion transfer barriers and increasing Li-ion conductivity, while Al doping lowers the Li chemical potential by 0.08 eV, reducing Li-ion conductivity. To determine the cause of Li chemical potential variations, we performed a combined analysis of the projected density of states, charge density, and Bader charge. The distinct charge distribution from dopant atoms to neighboring O atoms is critical for determining the Li-ion chemical potential. Ga and Fe dopants retain more electrons, which consequently makes the adjacent O atoms acquire a more positive charge that destabilizes Li ions by reducing the restraining force acting on them, thereby enhancing Li-ion conductivity. In contrast, Al doping transfers more electrons to neighboring O atoms, resulting in greater attraction forces to Li ions and reducing Li-ion conductivity. Additionally, Fe-doped LLZO exhibits extra states in the bandgap, potentially causing Fe reduction, as observed in experiments. Our findings provide valuable insights into the design of solid electrolytes and highlight the importance of the local charge distribution around the dopant and Li atoms in determining Li-ion conductivity. This insight could serve as a guiding principle for future materials design and optimization in solid-state electrolyte systems.

Purity monitor and TPC design for Xenoscope

The Xenoscope detector has the main goal of achieving electron drift over a 2.6 m distance, which is the scale of the future multi-ton scale dual-phase liquid xenon (LXe) TPCs for dark matter and rare event searches. The DARWIN experiment aims to have 40 tons of LXe as its active volume, reaching the neutrino floor background. Xenoscope will serve as a facility for photosensors and future technologies testing, in order to develop the next generation of LXe dark matter detectors. Metre-scale drift lengths will require a precise monitoring of the LXe purity. In this context, we have designed an integrated xenon purity monitor and a TPC, with the fabrication of the former nearly complete. We have characterised the electronics for charge readout, as well as different photocathode materials to optimise the charge yield and thus increase the precision in the purity measurement.

Simulation of charge accumulation in silicon photomultipliers under the influence of soft X-rays

A model of the cell structure of silicon photomultipliers (SiPM) is herein created in the software complex “Silvaco”. The cells are n+–p–p+-structures optically isolated from each other. The optical isolation of the cells is realized by trenches filled with metal after passivation of the walls with a SiO2 layer. Simulations are carried out for two variants of SiPM structures when the trench metal is electrically connected to the n+- (the first design) or p+ (the second design) region of the cell. The cells are irradiated by X-ray quanta with 10 keV energy up to a dose of 105 rads at the reverse bias values of Ub = –30 V (active electrical mode) and Ub = 0 V (passive electric mode). We obtain the distribution of the volume density of the accumulated charge Q in the oxide layer of the separation trench. It is established that the maximal Q value depends upon the irradiation mode. In the passive mode, the Q value is minimal and similar for both variants of the structures. In the active mode, Q increases in comparison to the passive mode by 2.5 times for SiPM with the structure of the second variant and by 5.9 times for the structure of the first variant. The obtained result can be explained by an increase of the hole charge yield under the influence of the appropriately distributed electric fields in the oxide layers of the separating trenches of the investigated SiPM’s cells.

Fluorescent Tracers for In Vivo Imaging of Lymphatic Targets.

The lymphatic system continues to gain importance in a range of conditions, and therefore, imaging of lymphatic vessels is becoming more widespread for research, diagnosis, and treatment. Fluorescent lymphatic imaging offers advantages over other methods in that it is affordable, has higher resolution, and does not require radiation exposure. However, because the lymphatic system is a one-way drainage system, the successful delivery of fluorescent tracers to lymphatic vessels represents a unique challenge. Each fluorescent tracer used for lymphatic imaging has distinct characteristics, including size, shape, charge, weight, conjugates, excitation/emission wavelength, stability, and quantum yield. These characteristics in combination with the properties of the target tissue affect the uptake of the dye into lymphatic vessels and the fluorescence quality. Here, we review the characteristics of visible wavelength and near-infrared fluorescent tracers used for in vivo lymphatic imaging and describe the various techniques used to specifically target them to lymphatic vessels for high-quality lymphatic imaging in both clinical and pre-clinical applications. We also discuss potential areas of future research to improve the lymphatic fluorescent tracer design.

Ionization yield measurement in a germanium CDMSlite detector using photo-neutron sources

Two photo-neutron sources, Y88Be9 and Sb124Be9, have been used to investigate the ionization yield of nuclear recoils in the CDMSlite germanium detectors by the SuperCDMS collaboration. This work evaluates the yield for nuclear recoil energies between 1 and 7 keV at a temperature of ∼ 50 mK. We use a geant4 simulation to model the neutron spectrum assuming a charge yield model that is a generalization of the standard Lindhard model and consists of two energy dependent parameters. We perform a likelihood analysis using the simulated neutron spectrum, modeled background, and experimental data to obtain the best fit values of the yield model. The ionization yield between recoil energies of 1 and 7 keV is shown to be significantly lower than predicted by the standard Lindhard model for germanium. There is a general lack of agreement among different experiments using a variety of techniques studying the low energy range of the nuclear recoil yield, which is most critical for interpretation of direct dark matter searches. This suggests complexity in the physical process that many direct detection experiments use to model their primary signal detection mechanism and highlights the need for further studies to clarify underlying systematic effects that have not been well understood up to this point.1 MoreReceived 15 February 2022Accepted 20 May 2022DOI:https://doi.org/10.1103/PhysRevD.105.122002© 2022 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasElectron-ion collisionsElectroweak interactions in nuclear physicsLow & intermediate energy heavy-ion reactionsParticle dark matterNuclear PhysicsGravitation, Cosmology & Astrophysics

New Strategy for Improved Conductivity and Redox-Enhanced Supercapacitor Performance of Nickel Metal-Organic Framework

Owing to the high-surface area and macromolecular architecture, metal-organic frame (MOF) material has been referred to as an advanced system for supercapacitor applications. Indeed, poor electrical property and structural instability under electrified conditions are the major limitations. In this work, we wish to introduce a new strategy for marked enhancement in the electrical and redox property of the MOF by simple chemical mixing followed by ultrasonication of pristine MOF with low-cost carbon black (CB) material. As a model system, Ni-MOF, prepared using 2,2’-bipyridine and benzene-1,4-dicarboxylic acid (provides a rich source for π-π interaction with graphic carbon), functionalized CB, designated as CB@Ni-MOF, has been developed for improved energy storage application. Electrochemical studies of CB@Ni-MOF modified screen-printed carbon electrode showed about ten times enhanced peak current and surface excess value (24.8 nmol.cm−2) over the respective pristine Ni-MOF modified electrode (1.9 nmol.cm−2) in 1 M NaOH solution. Physicochemical and electrochemical characterization using TEM, X-ray, Raman, FTIR, BET Surface area and electrochemical impedance measurements collectively revealed that there are multiple hydrogen-bonding interactions between the oxygen functional groups of Ni-MOF and CB, and strong π-π interaction between the aromatic units of Ni-MOF and sp2 carbon-graphitic sites of CB. These interactions help de-agglomeration and active-site inter-connection and a marked reduction in the multi-shell hollow structure of the CB (55nm→30nm). Capacitance measurement by galvanostatic charge and discharge (GCD) method yield value, 2700 F g−1 at a biased-current, 2 A g−1. It is about seven times higher than the values obtained with the respective pristine Ni-MOF (415 F g−1) and markedly higher than several literature-based MOF values. A GCD cyclic stability of the CB@Ni-MOF showed about 2% and 10% decrement at 2000 and 5000 cycles, respectively.

Performance of the ReD TPC, a novel double-phase LAr detector with silicon photomultiplier readout

A double-phase argon Time Projection Chamber (TPC), with an active mass of 185 g, has been designed and constructed for the Recoil Directionality (ReD) experiment. The aim of the ReD project is to investigate the directional sensitivity of argon-based TPCs via columnar recombination to nuclear recoils in the energy range of interest (20–200,hbox {keV}_{nr}) for direct dark matter searches. The key novel feature of the ReD TPC is a readout system based on cryogenic Silicon Photomultipliers (SiPMs), which are employed and operated continuously for the first time in an argon TPC. Over the course of 6 months, the ReD TPC was commissioned and characterised under various operating conditions using gamma -ray and neutron sources, demonstrating remarkable stability of the optical sensors and reproducibility of the results. The scintillation gain and ionisation amplification of the TPC were measured to be g_1 = (0.194 pm 0.013) photoelectrons/photon and g_2 = (20.0 pm 0.9) photoelectrons/electron, respectively. The ratio of the ionisation to scintillation signals (S2/S1), instrumental for the positive identification of a candidate directional signal induced by WIMPs, has been investigated for both nuclear and electron recoils. At a drift field of 183 V/cm, an S2/S1 dispersion of 12% was measured for nuclear recoils of approximately 60–90,hbox {keV}_{nr}, as compared to 18% for electron recoils depositing 60 keV of energy. The detector performance reported here meets the requirements needed to achieve the principal scientific goals of the ReD experiment in the search for a directional effect due to columnar recombination. A phenomenological parameterisation of the recombination probability in LAr is presented and employed for modeling the dependence of scintillation quenching and charge yield on the drift field for electron recoils between 50–500 keV and fields up to 1000 V/cm.

Short Excited-State Lifetimes Mediate Charge-Recombination Losses in Organic Solar Cell Blends with Low Charge-Transfer Driving Force.

A blend of a low-optical-gap diketopyrrolopyrrole polymer and a fullerene derivative, with near-zero driving force for electron transfer, is investigated. Using femtosecond transient absorption and electroabsorption spectroscopy, the charge transfer (CT) and recombination dynamics as well as the early-time transport are quantified. Electron transfer is ultrafast, consistent with a Marcus-Levich-Jortner description. However, significant charge recombination and unusually short excited (S1 ) and CT state lifetimes (≈14ps) are observed. At low S1 -CT offset, a short S1 lifetime mediates charge recombination because: i) back-transfer from the CT to the S1 state followed by S1 recombination occurs and ii) additional S1 -CT hybridization decreases the CT lifetime. Both effects are confirmed by density functional theory calculations. In addition, relatively slow (tens of picoseconds) dissociation of charges from the CT state is observed, due to low local charge mobility. Simulations using a four-state kinetic model entailing the effects of energetic disorder reveal that the free charge yield can be increased from the observed 12% to 60% by increasing the S1 and CT lifetimes to 150ps. Alternatively, decreasing the interfacial CT state disorder while increasing bulk disorder of free charges enhances the yield to 65% in spite of the short lifetimes.

Measurement of the ionization yield of neutron-induced proton recoils in Tetramethylsilane

We report on a low energy measurement of the ionization yield in a Tetramethylsilane Time Projection Chamber (TPC) using 2.8 MeV neutrons from a deuterium-deuterium neutron generator. The proton recoil charge yield is measured at four different electric fields, finding a dependence that can be described by the Thomas-Imel model. By comparing the proton recoil yield to that obtained from γ-ray calibrations, a quenching factor is obtained for each electric field. These results demonstrate the feasibility of using room temperature organic ionisation detectors to detect MeV-scale neutrons in the proton-recoil channel.