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Surface Passivation of Perovskite Solar Cells Toward Improved Efficiency and Stability
摘要： The advancement of perovskite solar cells (PVSCs) technology toward commercialized promotion needs high efficiency and optimum stability. By introducing a small molecular material such as tetratetracontane (TTC, CH3(CH2)42CH3) at the fullerene (C60)/perovskite interface of planar p-i-n PVSCs, we significantly reduced the interfacial traps, thereby suppressing electron recombination and facilitating electron extraction. Consequently, an improved efficiency of 20.05% was achieved with a high fill factor of 79.4%, which is one of the best performances for small molecular-modified PVSCs. Moreover, the hydrophobic TTC successfully protects the perovskite film from water damage. As a result, we realized a better long-term stability that maintains 87% of the initial efficiency after continuous exposure for 200 h in air.
关键词： Surface defect,Charge transport,Surface passivation,Perovskite solar cells
更新于2025-11-21 11:01:37
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Photophysical features and semiconducting properties of propeller-shaped oligo(styryl)benzenes
摘要： Electronic, optical, and semiconducting properties of a series of propeller-shaped oligo(styryl)benzenes have been systematically investigated to monitor the effect of the number of styryl branches (three, four, and six) around a central benzene core. In order to clarify the relationships between their structures and properties, Density Functional Theory calculations were carried out at several levels of theory considering solvents with different polarity. Absorption and vibrational Raman spectroscopies showed that cruciform, four-branched derivatives present the most effective π-conjugation in agreement with the lowest calculated bond length alternation and bandgap. Deviations from the mirror image symmetry between absorption and fluorescence spectra were related to changes in the molecular conformation upon electronic excitation. Furthermore, in order to investigate the semiconducting behavior of oligo(styryl)benzenes, molecular structure changes and different electronic properties related to ionization processes were calculated and analyzed. Hole and electron reorganization energies were also computed to provide a first approximation on the n- or p-type character of these compounds. In some cases, electron reorganization energies comparable to common n-type semiconductors were found.
关键词： photophysical properties,Density Functional Theory,charge transport,Raman spectroscopy,oligo(styryl)benzenes,semiconducting properties
更新于2025-11-20 15:33:11
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New insights into active-area-dependent performance of hybrid perovskite solar cells
摘要： The morphology of hybrid perovskite thin films depends strongly on the processing parameters due to its complex crystallization kinetics from a solution to solid perovskite halide phase. It is also profoundly sensitive to the device area of the deposited thin film, and hence reproducible photoconversion efficiency (PCE) remained a bottleneck for the fabrication of efficient photovoltaic devices having large active area. The present work focuses on the investigations of the relationship between perovskite ink concentration-dependent quality of the perovskite overlayer and PCE of the perovskite solar cells (PSC) while scaling-up process. The field-emission scanning electron microscopy images revealed that the surface coverage of perovskite overlayer depends on the concentration of perovskite solution and device area. The active-area-dependent current density (J)-voltage (V) and external quantum efficiency measurements identify morphology-dependent variation in charge-transport/recombination pathways. We confirmed that among different precursor concentrations, 40 wt% perovskite ink is suitable to produce uniform perovskite overlayer over 1 cm2. As a result, highly reproducible PCE * 13% has been achieved for the PSC having an active area of 1 cm2. Overall, our findings significantly provide new insights into the active-area-dependent PCE of PSC.
关键词： morphology,hybrid perovskite,charge-transport,photoconversion efficiency,solar cells,recombination pathways
更新于2025-11-19 16:56:42
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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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Mobility Evaluation of BTBT Derivatives: Limitation and Impact on Charge Transport
摘要： Amongst contemporary semiconductors many of the best performing materials are based on [1]benzothieno[3,2-b][1]benzothiophene (BTBT). Alkylated derivatives of these small molecules not only provide high hole mobilities but can also be easily processed by thermal vacuum or solution deposition methods. Over the last decade numerous publications have been investigating molecular structures and charge transport properties to elucidate what makes these molecules so special. However, the race towards ever higher mobilities resulted in significantly deviating values, which exacerbates linking molecular structure to electronic properties. Moreover, a recently arisen debate on overestimation of organic field-effect transistor mobilities calls for a revaluation of these numbers. We synthesised and characterised four BTBT derivatives with either one or two alkyl chains (themselves consisting of either eight or ten carbon atoms), and investigated their spectroscopic, structural and electrical properties. By employing two probes, gated 4-point probe and gated van der Pauw measurements, we compare field effect mobility values at room and low temperatures, and discuss their feasibility and viability. We attribute mobility changes to different angles between molecule planes and core-to-core double layer stacking of asymmetric BTBT derivatives and show higher mobilities in the presence of more and longer alkyl chains. A so called “zipper effect” brings BTBT cores in closer proximity promoting stronger intermolecular orbital coupling and hence higher charge transport.
关键词： charge transport,mobility,BTBT,organic electronics,organic transistors
更新于2025-10-23 16:08:52
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Manipulation of Charge Transport by Metallic V <sub/>13</sub> O <sub/>16</sub> Decorated on Bismuth Vanadate Photoelectrochemical Catalyst
摘要： Conductive metal oxides represent a new category of functional material with vital importance for many modern applications. The present work introduces a new conductive metal oxide V13O16, which is synthesized via a simplified photoelectrochemical procedure and decorated onto the semiconducting photocatalyst BiVO4 in controlled mass percentages ranging from 25% to 37%. Owing to its excellent conductivity and good compatibility with oxide materials, the metallic V13O16-decorated BiVO4 hybrid catalyst shows a high photocurrent density of 2.2 ± 0.2 mA cm?2 at 1.23 V versus reversible hydrogen electrode (RHE). Both experimental characterization and density functional theory calculations indicate that the superior photocurrent derives from enhanced charge separation and transfer, resulting from ohmic contact at the interface of mixed phases and superior electrical conductivity from V13O16. A Co–Pi coating on BiVO4–V13O16 further increases the photocurrent to 5.0 ± 0.5 mA cm?2 at 1.23 V versus RHE, which is among the highest reported for BiVO4-based photoelectrodes. Surface photovoltage and transient photocurrent measurements suggest a charge-transfer model in which photocurrents are enhanced by improved surface passivation, although the barrier at the Co–Pi/electrolyte interface limits the charge transfer.
关键词： charge transport,bismuth vanadate,Co–Pi passivation,water oxidation,metallic V13O16
更新于2025-09-23 15:23:52
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Modulated anodization synthesis of Sn-doped iron oxide with enhanced solar water splitting performance
摘要： Modulated anodization synthesis is introduced here for the fabrication of porous Sn-doped iron oxide. Continuous square-wave modulation consisting of highly positive (+50 to +80 V range) and slightly negative potentials (-2 to -10 V range) at 100 Hz allowed the etching anodization of the metallic Fe foil and incorporation of Sn-dopant from the fluoride anion-containing electrolyte, respectively. Compared with the undoped iron oxide, the surface-enriched Sn-dopant (in the form of Sn4+) alleviates the trapping and recombination of surface holes, while enhancing the hole transfer at the surface states. As such, the overpotential for photoelectrochemical (PEC) water oxidation was reduced by 110 mV and photocurrent density doubled. The incorporation of Co-Pi co-catalyst further improved the hole transfer efficiency, resulting in further reduction in overpotential by another 330 mV with respect to the bare Sn-doped iron oxide and significant improvement in photocurrent density at potentials below +1.23 V vs. reversible hydrogen electrode. Lastly, the iron oxide electrodes exhibit highly stable PEC water oxidation with no degradation in activity throughout the 10 h assessment under simulated solar irradiation and Faradaic efficiency of 90%. We envisage that the modulated anodization technique can be conveniently incorporated for a wide range of other dopants in search of efficient solar water splitting electrodes.
关键词： Doping,Hematite,Hydrogen,Photoelectrochemical water splitting,Charge transport
更新于2025-09-23 15:23:52
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Theory for IMPS on Rough and Finite Fractal Dye Sensitized Solar?Cell
摘要： A generalized theoretical model of intensity modulated photocurrent spectroscopy (IMPS) for the random morphology in a dye sensitized solar cell (DSSC) under uniform illumination is developed. The generalized IMPS expression for the disordered semiconducting/conducting glass interface of a DSSC is obtained in term of power spectral density of roughness. Influence of surface roughness on the dynamic response of DSSC originate due to the coupling of characteristic phenomenological and morphological length scales. A detailed analysis of IMPS response is performed over finite self-affine fractals to highlight roughness induced anomalies and cause of photocurrent enhancement. The IMPS of a rough DSSC exhibit three characteristic frequency regimes: lifetime of charge carrier dependent low frequency regime, surface irregularity dependent intermediate power-law regime and diffusion controlled high frequency regime. Finally, our theory facilitates the understanding of dynamics and kinetics of charge carriers under the influence of ubiquitous surface disorder.
关键词： DSSC,charge transport,fractal,surface roughness,IMPS
更新于2025-09-23 15:23:52
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Charge transport in graphene-based mesoscopic realizations of Sachdev-Ye-Kitaev models
摘要： We consider a recent proposal for a physical realization of the Sachdev-Ye-Kitaev (SYK) model in the zeroth-Landau-level sector of an irregularly shaped graphene flake. We study in detail charge transport signatures of the unique non-Fermi-liquid state of such a quantum dot coupled to noninteracting leads. The properties of this setup depend essentially on the ratio p between the number of transverse modes in the lead M and the number of the fermion degrees of freedom N on the SYK dot. This ratio can be tuned via the magnetic field applied to the dot. Our proposed setup gives access to the nontrivial conformal-invariant regime associated with the SYK model as well as a more conventional Fermi-liquid regime via tuning the field. The dimensionless linear-response conductance acquires distinct p dependencies for the two phases, respectively, in the low-temperature limit, with a universal jump at the transition. We find that corrections scale linearly and quadratically in either temperature or frequency on the two sides of the transition. In the weak-tunneling regime, we find differential conductance proportional to the inverse square root of the applied voltage bias U for bias energy eU larger than temperature scale kB T. This dependence is replaced by a conventional Ohmic behavior with constant conductance proportional to 1/sqrt(T) for bias energy eU smaller than temperature scale kB T. We also describe the out-of-equilibrium current-bias characteristics and discuss various crossovers between the limiting behaviors mentioned above.
关键词： Sachdev-Ye-Kitaev model,tunneling conductance,graphene,quantum dot,charge transport,non-Fermi-liquid,conformal invariance
更新于2025-09-23 15:23:52
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Long-Range Activationless Photostimulated Charge Transport in Symmetric Molecular Junctions
摘要： Molecular electronic junctions consisting of nitroazobenzene oligomers covalently bonded to a conducting carbon surface using an established 'all-carbon' device design were illuminated with UV?vis light through a partially transparent top electrode. Monitoring junction conductance with a DC bias imposed permitted observation of photocurrents while varying the incident wavelength, intensity, molecular layer thickness, and temperature. The photocurrent spectrum tracked the in situ absorption spectrum of nitroazobenzene, increased linearly with light intensity, and depended exponentially on applied bias. The electronic characteristics of the photocurrent differed dramatically from those of the same device in the dark, with orders of magnitude higher conductance and very weak attenuation with molecular layer thickness (β = 0.14 nm?1 for thickness above 5 nm). The temperature dependence of the photocurrent was opposite that of the dark current, with a 35% decrease in conductance between 80 and 450 K, while the dark current increased by a factor of 4.5 over the same range. The photocurrent was similar to the dark current for thin molecular layers but greatly exceeded the dark current for low bias and thick molecular layers. We conclude that the light and dark mechanisms are additive, with photoexcited carriers transported without thermal activation for a thickness range of 5?10 nm. The inverse temperature dependence is likely due to scattering or recombination events, both of which increase with temperature and in turn decrease the photocurrent. Photostimulated resonant transport potentially widens the breadth of conceivable molecular electronic devices and may have immediate value for wavelength-specific photodetection.
关键词： charge transport,optoelectronics,photocurrent,molecular electronics,molecular orbital energy,tunneling barrier,HOMO?LUMO gap,photoinduced transport
更新于2025-09-23 15:22:29