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Charge transport and electron recombination suppression in dye-sensitized solar cells using graphene quantum dots
摘要： In this study, TiO2 photoelectrodes were sensitized in different concentration of Graphene Quantum Dots (GQDs) solution to enhance photovoltaic performance and charge transport of DSSC. The performance of pristine TiO2 and TiO2-GQDs photoelectrodes were compared to investigate the effect of GQDs incorporation in DSSC. It was found GQDs increased light absorption of TiO2 photoelectrode at visible spectrum in the range of λ = 375 nm to λ = 600 nm, resulting highest current–density, Jsc and photon-to-current conversion efficiency, ?c. Solar cell sensitized in 7.5 mg/ml concentration of GQDs known as (PG 7.5) cell shown the highest reading by 15.49 mA cm?2 and 6.97%, which indicated an improvement by 28.07% and 70.83% for Jsc and ? compare to pristine TiO2 DSSC at 12.10 mA cm?2 and 4.08%. Photoluminescence property own by GQDs may enhance photon emission to visible region when uv-ray excited on solar cell. Thus, generate more electron-hole pairs in the photoelectrode and enhance the photovoltaic parameters of DSSC. PG 7.5 cell also exhibited lowest series resistance (Rs) of 36.60 Ω, highest charge transfer resistance (Rct2) of 41.98 Ω and electron lifetime of 6.33 ms among other DSSC. These possibly due to suppression of recombination between TiO2/dye/electrolyte interfaces. Hence, resulting highest charge collection efficiency (CCE) of 53.42%. The EIS analysis confirmed the PV performance of the best cell of PG 7.5 since the same cell also generated the best photon-current conversion efficiency (PCE). This study revealed GQDs can enhanced photovoltaic parameter and charge collection efficiency of DSSC.
关键词： Charge collection efficiency,GQDs-DSSC,TiO2-GQDs,Charge transport
更新于2025-11-14 17:04:02
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Design and Implementation of Digital Phase Locked Loop for Single-Phase Grid-Tied PV Inverters
摘要： The rational design of porphyrin sensitizers is always crucial for dye-sensitized solar cells (DSSCs), since the change of only a single atom can have a significant influence on the photovoltaic performance. We incorporated the pyridothiadiazole group, as a stronger electron-withdrawing group, into the commonly well-established skeleton of D-porphyrin-triple bond-acceptor sensitizers by a single atom change for a well-known strong electron-withdrawing benzothiadiazole (BTD) unit as an auxiliary acceptor. The impact of the pyridothiadiazole group on the optical; electrochemical; and photovoltaic properties of D–π–A porphyrin sensitizers was investigated with comparison for a benzothiadiazole-substituted SGT-020 porphyrin. The pyridothiadiazole-substituted SGT-024 porphyrin dye was red-shifted so that the absorption range might be expected to achieve higher light harvest efficiency (LHE) than the SGT-020 porphyrin. However, all the devices were fabricated by utilizing SGT-020 and SGT-024, evaluated and found to achieve a cell efficiency of 10.3% for SGT-020-based DSSC but 4.2% for SGT-024-based DSSC under standard global AM 1.5G solar light conditions. The main reason is the lower charge collection efficiency of SGT-024-based DSSC than SGT-020-based DSSC, which can be attributed to the tilted dye adsorption mode on the TiO2 photoanode. This may allow for faster charge recombination, which eventually leads to lower Jsc, Voc and power conversion efficiency (PCE).
关键词： D–π–A structural porphyrin,charge collection efficiency,acceptor units,charge recombination,dye-sensitized solar cells
更新于2025-09-23 15:23:52
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Novel fused-silica charge detection tile for particle detectors
摘要： Purpose Develop a novel charge-detecting tile for future large-scale liquid xenon TPC for searching for neutrinoless double-beta decay. Methods Use advanced microelectronic technologies to fabricate small metal pads on a fused-silica wafer. The pads are chained into orthogonal strips, and the strips are isolated at the cross sections. The size of the pads de?nes the pitch between parallel strips and can be ?exibly tuned according to any optimized dimension from future Monte Carlo studies. Such tile also has good potential to suppress the radioactivity and control electronics noise. Furthermore, its modular design allows to easily cover a large size. Results The design and performance have been demonstrated by a prototype tile, particularly by comprehensive tests in liquid xenon. Conclusions A new design of charge detection tile and the fabrication technologies have been developed, which would be useful for future noble liquid detectors.
关键词： Time projection chamber (TPC),Double-beta decay,Microelectronic processing,Charge collection
更新于2025-09-23 15:23:52
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On the Question of the Need for a Built-In Potential in Perovskite Solar Cells
摘要： Perovskite semiconductors as the active materials in efficient solar cells exhibit free carrier diffusion lengths on the order of microns at low illumination fluxes and many hundreds of nanometers under 1 sun conditions. These lengthscales are significantly larger than typical junction thicknesses, and thus the carrier transport and charge collection should be expected to be diffusion controlled. A consensus along these lines is emerging in the field. However, the question as to whether the built-in potential plays any role is still of matter of some conjecture. This important question using phase-sensitive photocurrent measurements and theoretical device simulations based upon the drift-diffusion framework is addressed. In particular, the role of the built-in electric field and charge-selective transport layers in state-of-the-art p–i–n perovskite solar cells comparing experimental findings and simulation predictions is probed. It is found that while charge collection in the junction does not require a drift field per se, a built-in potential is still needed to avoid the formation of reverse electric fields inside the active layer, and to ensure efficient extraction through the charge transport layers.
关键词： perovskite solar cells,charge collection,built-in potential,charge transport layers
更新于2025-09-23 15:19:57
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The Effect of Titanium (IV) Chloride Surface Treatment to Enhance Charge Transport and Performance of Dye-Sensitized Solar Cell
摘要： In this study, the photovoltaic and electrochemical characteristics of the dye-sensitised solar cell (DSSC) after Titanium (IV) Chloride (TiCl4) treatment on a TiO2 photoelectrode were investigated. Photoelectrodes of untreated, pre-TiCl4 and post-TiCl4 treatment were prepared to form a complete DSSC. The photoelectrode was sensitised in 40mM of TiCl4 solution at 80 °C for 30 minutes, and then it is sintered at 500 °C. The morphology of photoelectrodes has been studied using FESEM, and it was found that, after TiCl4 treatment, the particle necking and particle size of TiO2 nanoparticles were increased significantly. Therefore, it improved the electron transfer path on the TiO2 layer. Subsequently, the the light absorption intensity after post-TiCl4 treatments was increased due to strong adhesion and homogeneity of the TiO2 layer on the FTO substrate, which results in higher current density and photon-conversion efficiency by 18.95 mAcm-2 and 8.03% when compared to an untreated electrode at 12.1 mAcm-2 and 4.08% (increment of 56.7% and 96.9%), respectively. Electrochemical impedance spectroscopy used to study the internal electrochemical characteristics of DSSC after the treatment. Thus, it proves that the treatment suppresses the charge recombination between TiO2 and the electrolyte interface by increasing charge transfer resistance after post-TiCl4 treatment by 24.06Ω from 16.11Ω for untreated photoelectrodes (increment of 49.39%). The electron lifetime also improved from 0.4 to 1.59 ms, which results in the enhancement of charge collection efficiency after post-treatment by 31.09% compared to the untreated electrode. Improvement of charge collection efficiency indicated that the TiCl4 treatment had played an important role in charge separation and charge collection on the TiO2 and electrolyte interface of DSSC.
关键词： charge transport,DSSC surface treatment,TiCl4,charge collection efficiency (CCE)
更新于2025-09-19 17:13:59
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The impact of laser energy, bias and irradiation positions on single event transients of InP HBT
摘要： The mechanism of single event transients in indium phosphide heterojunction bipolar transistors are studied with different laser energy, collector and irradiation positions based on a pulsed laser experiment. The area of the depletion region neutralized by the laser track determines the area of the funnel region, and affects the total charges collected by collector QTotal. The total charge collection consists of the charge collected in the depletion region, the charges collected in funnel region, and the diffusion charges. The larger the area of the neutralized depletion region, the larger the area of the funnel region, thus, the more electron–hole pairs would be collected. The influence of laser energy, collector bias and irradiation positions on total charge collection is studied and discussed in detail.
关键词： transient current,single event transient,charge collection mechanism,pulsed laser
更新于2025-09-16 10:30:52
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Tail state limited photocurrent collection of thick photoactive layers in organic solar cells
摘要： We analyse organic solar cells with four different photoactive blends exhibiting differing dependencies of short-circuit current upon photoactive layer thickness. These blends and devices are analysed by transient optoelectronic techniques of carrier kinetics and densities, air photoemission spectroscopy of material energetics, Kelvin probe measurements of work function, Mott-Schottky analyses of apparent doping density and by device modelling. We conclude that, for the device series studied, the photocurrent loss with thick active layers is primarily associated with the accumulation of photo-generated charge carriers in intra-bandgap tail states. This charge accumulation screens the device internal electrical field, preventing efficient charge collection. Purification of one studied donor polymer is observed to reduce tail state distribution and density and increase the maximal photoactive thickness for efficient operation. Our work suggests that selecting organic photoactive layers with a narrow distribution of tail states is a key requirement for the fabrication of efficient, high photocurrent, thick organic solar cells.
关键词： tail states,charge carriers,photoactive blends,organic solar cells,charge collection
更新于2025-09-12 10:27:22
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Perovskite solar cells with a hybrid electrode structure
摘要： Perovskite solar cells (PSCs) with a novel hybrid electrode structure, in which a single device can operate with either a vertical (sandwich) or lateral (back-contact) configuration of contacts, are demonstrated in this work. The hybrid structure was achieved by depositing an additional anode on top of a prefabricated back-contact PSC device, giving a final device with three electrodes—one shared cathode and two anodes. Device performances are tested and evaluated for both operation modes, and a semianalytical model along with coupled optoelectronic simulations is used to rationalize the experimental results. It is determined that due to the intrinsically narrow depletion region near the contact interfaces, the charge collection efficiency in the back-contact device structure appears to be significantly lower compared to the sandwich device structure. This finding provides an insight into the cause of the performance disparity between these two architectures.
关键词： Perovskite solar cells,charge collection efficiency,hybrid electrode structure,back-contact,sandwich configuration
更新于2025-09-12 10:27:22
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Significant Influence of a Single Atom Change in Auxiliary Acceptor on Photovoltaic Properties of Porphyrin-Based Dye-Sensitized Solar Cells
摘要： The rational design of porphyrin sensitizers is always crucial for dye-sensitized solar cells (DSSCs), since the change of only a single atom can have a signi?cant in?uence on the photovoltaic performance. We incorporated the pyridothiadiazole group, as a stronger electron-withdrawing group, into the commonly well-established skeleton of D-porphyrin-triple bond-acceptor sensitizers by a single atom change for a well-known strong electron-withdrawing benzothiadiazole (BTD) unit as an auxiliary acceptor. The impact of the pyridothiadiazole group on the optical; electrochemical; and photovoltaic properties of D–π–A porphyrin sensitizers was investigated with comparison for a benzothiadiazole-substituted SGT-020 porphyrin. The pyridothiadiazole-substituted SGT-024 porphyrin dye was red-shifted so that the absorption range might be expected to achieve higher light harvest ef?ciency (LHE) than the SGT-020 porphyrin. However, all the devices were fabricated by utilizing SGT-020 and SGT-024, evaluated and found to achieve a cell ef?ciency of 10.3% for SGT-020-based DSSC but 4.2% for SGT-024-based DSSC under standard global AM 1.5G solar light conditions. The main reason is the lower charge collection ef?ciency of SGT-024-based DSSC than SGT-020-based DSSC, which can be attributed to the tilted dye adsorption mode on the TiO2 photoanode. This may allow for faster charge recombination, which eventually leads to lower Jsc, Voc and power conversion ef?ciency (PCE).
关键词： charge collection ef?ciency,dye-sensitized solar cells,D–π–A structural porphyrin,acceptor units,charge recombination
更新于2025-09-11 14:15:04
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Substrate Effects on Charge Carrier Transport Properties of Single-Crystal CVD Diamonds and an 8?mm Square Radiation Energy Spectrometer
摘要： In an effort to enlarge a sensitive area of a diamond radiation energy spectrometer, a self-standing chemical vapor deposition (CVD) single crystal is grown on an 8-mm-square “general grade” CVD single-crystal diamond substrate fabricated by Element Six Ltd. The growth conditions that achieved a μτ product of 3 × 10?4 cm2 V?1 for holes in a CVD single-crystal diamond grown on a high-pressure and high-temperature (HP/HT) type IIa single-crystal diamond substrate elsewhere are adopted. The charge collection efficiency (CCE) of 99.9% for both charge carriers, and 0.39% and 0.5% of energy resolution for holes and electrons are achieved using 5.486 MeV alpha particles. Uniformity of the energy resolution is sufficient for the use of a radiation energy spectrometer. However, μτ products of (5.0 ± 0.4) × 10?5 and (1.8 ± 0.2) × 10?5 cm2 V?1 for holes and electrons are obtained, respectively. These values are approximately one order of magnitude smaller than the μτ products of the CVD single crystal grown on a HP/HT type IIa diamond substrate using the same growth conditions.
关键词： charge collection efficiency,μτ products,energy resolution,radiation detector,homogeneity
更新于2025-09-09 09:28:46