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Understanding the Impact of Cu-In-Ga-S Nanoparticles Compactness on Holes Transfer of Perovskite Solar Cells
摘要： Although a compact holes-transport-layer (HTL) ?lm has always been deemed mandatory for perovskite solar cells (PSCs), the impact their compactness on the device performance has rarely been studied in detail. In this work, based on a device structure of FTO/CIGS/perovskite/PCBM/ZrAcac/Ag, that effect was systematically investigated with respect to device performance along with photo-physics characterization tools. Depending on spin-coating speed, the grain size and coverage ratio of those CIGS ?lms on FTO substrates can be tuned, and this can result in different hole transfer ef?ciencies at the anode interface. At a speed of 4000 r.p.m., the band level offset between the perovskite and CIGS modi?ed FTO was reduced to a minimum of 0.02 eV, leading to the best device performance, with conversion ef?ciency of 15.16% and open-circuit voltage of 1.04 V, along with the suppression of hysteresis. We believe that the balance of grain size and coverage ratio of CIGS interlayers can be tuned to an optimal point in the competition between carrier transport and recombination at the interface based on the proposed mechanism. This paper de?nitely deepens our understanding of the hole transfer mechanism at the interface of PSC devices, and facilitates future design of high-performance devices.
关键词： perovskite solar cells,compactness,Cu-In-Ga-S,hole transfer,holes transport layer,recombination
更新于2025-11-21 10:59:37
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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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Role of interface potential barrier, Auger recombination and temporal coherence in In <sub/>0.5</sub> Ga <sub/>0.5</sub> As/GaAs quantum dot-based p-i-n light emitting diodes
摘要： In this work, we investigate the mechanisms that control the electroluminescence from p-i-n heterostructures containing self-assembled In0.5Ga0.5As quantum dots embedded inside a GaAs/Al0.3Ga0.7As quantum well as a function of temperature and applied bias. Our results reveal that the carrier dynamics at the interface between the quantum dot and the quantum well play a crucial role in the electroluminescence emission. At low temperatures, two distinct emission bands are observed. Initially at low bias current, we observe broad emissions from the quantum wells and wetting layers. Another dominant and sharp emission at lower energy arises from the quantum dots, but only at higher bias currents. We discuss how a potential barrier between the quantum dots and quantum well can control the density of injected carriers undergoing optical recombination. We have also investigated the role of carrier capture and escape, quantum-confined stark effect and band-filling effects in the electroluminescence emission. In addition, we demonstrate how measurements of temporal coherence of individual spectral peaks, can detect the presence of Auger recombination in quantum dots under high injection currents. Interestingly, a significant increase in the temporal coherence of quantum dot emissions is observed, which could be due to a decrease in Auger recombination with increasing temperature.
关键词： quantum dots,Auger recombination,electroluminescence,coherence
更新于2025-11-14 17:28:48
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[IEEE 2017 IEEE 44th Photovoltaic Specialists Conference (PVSC) - Washington, DC (2017.6.25-2017.6.30)] 2017 IEEE 44th Photovoltaic Specialist Conference (PVSC) - Interface Effects of Alkali Treatment on Cu-Rich Thin Film Solar Cells
摘要： CuInSe2 absorbers grown under Cu-excess have better current collection compared to those grown as Cu-poor. However, cells based on Cu-excess absorbers show lower efficiency due to a worse absorber-buffer interface where the interface recombination is the dominant recombination path. In this paper, potassium fluoride post-deposition treatment is used to improve this interface, as evidenced by an activation energy of the main recombination path close to the band gap energy. The treatment also succeeded in eliminating the 200-meV step observed in admittance measurements; a main characteristic of Cu-excess CuInSe2 cells.
关键词： admittance measurements,Cu-excess,interface recombination,potassium fluoride post-deposition treatment,CuInSe2
更新于2025-11-14 17:28:48
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Improve the crystallinity and morphology of perovskite films by suppressing the formation of intermediate phase of CH3NH3PbCl3
摘要： Crystallinity and morphology of perovskite films can greatly influence the performance of perovskite solar cells (Pero-SCs) in terms of charge carrier generation and transportation. Incorporation of Cl (from either PbCl2 or CH3NH3Cl) in crystal growth of CH3NH3PbI3 is known as an effective method to acquire larger crystal grains and longer carrier diffusion length. It has been reported that an intermediate phase of CH3NH3PbCl3 was usually observed during crystallization, which should be critical to the quality of the resulting perovskite, however, how the intermediate phase influence the crystal growth was lack of comprehensive understanding. In this study, through varying the mixing ratio of the precursors PbI2:2CH3NH3I and PbCl2:3CH3NH3I, we were able to systematically tune the content and the converting time of CH3NH3PbCl3. We found that suppressing the formation of CH3NH3PbCl3 within the as-cast films can effectively improve the quality (crystallinity and morphology) of the resulting perovskite films. The improvement led to significant enhancement of the performance of the corresponding p-i-n planar Pero-SCs. Under optimized conditions, the best PCE was increased from 12.8% to 16.2%, which should be attributed to the alleviated charge recombination due to the improved quality of perovskite films by suppressing the formation of CH3NH3PbCl3.
关键词： morphology and crystallinity,perovskite solar cells,CH3NH3PbCl3,intermediate phase,charge recombination
更新于2025-11-14 15:13:28
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Effects of fluorination and thermal annealing on charge recombination processes in polymer bulk-heterojunction solar cells
摘要： We investigate the effect of fluorination on the photovoltaic properties of an alternating conjugated polymer composed of 4,8-di-2-thienylbenzo[1,2-b:4,5-b0]dithiophene and 4,7-bis([2,20-bithiophen]-5-yl)-benzo-2-1-3-thiadiazole (4TBT) units in bulk-heterojunction solar cells. The unsubstituted and fluorinated polymers afford very similar open-circuit voltages and fill factor values, but the fluorinated polymer performed better due to enhanced aggregation which provides a higher photocurrent. The photovoltaic performance of both materials improved upon thermal annealing at 150–200 °C as a result of a significantly increased fill factor and open-circuit voltage, counteracted by a slight loss in photocurrent. Detailed studies of the morphology, light intensity dependence, external quantum efficiency and electroluminescence allowed the exploration of the effects of fluorination and thermal annealing on the charge recombination and the nature of the donor–acceptor interfacial charge transfer states in these films.
关键词： polymer bulk-heterojunction solar cells,thermal annealing,charge recombination,fluorination,photovoltaic properties
更新于2025-10-22 19:40:53
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Contactless Optical Characterization of Carrier Dynamics in Free-Standing InAs-InAlAs Core-Shell Nanowires on Silicon
摘要： Contactless time-resolved pump-probe and external quantum efficiency measurements were performed on epitaxially grown free-standing wurtzite indium arsenide/indium aluminum arsenide (InAs-InAlAs) core-shell nanowires on Si (111) substrate from 77K to 293K. The first independent investigation of Shockley-Read-Hall, radiative and Auger recombination in InAs-based NWs is presented. Although the Shockley-Read Hall recombination coefficient was found to be at least two orders of magnitude larger than the average experimental values of other reported InAs materials, the Auger recombination coefficient was reported to be ten-fold smaller. The very low Auger and high radiative rates result in an estimated peak internal quantum efficiency of the core-shell nanowires as high as 22% at 77K, making these nanowires of potential interest for high efficiency mid-infrared emitters. A greater than two-fold enhancement in minority carrier lifetime was observed from capping nanowires with a thin InAlAs shell due to passivation of surface defects.
关键词： Auger recombination rate,radiative,Shockley-Read-Hall,Pump-probe spectroscopy,core-shell nanowires,surface/interface recombination velocity,minority carrier lifetime
更新于2025-09-23 15:23:52
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Radiative and non radiative recombinations study in the novel nanocomposites BiVO4/3DOM-TiO2, ZnO/3DOM-TiO2 and BiVO4/3DOM-ZnO: Application to the photocatalysis
摘要： A theoretical investigation of optical proprieties of three nanostructures such as BiOV4/3DOM TiO2, ZnO/3DOM TiO2 and BiOV4/3DOM ZnO has been presented and discussed. The study based on a one band effective mass approximation model was developed to calculate the charge carrier energies on various parameters of nanostructures including their size. We computed the optical properties for both spherical BiVO4 and ZnO nanoparticles incorporated in the three dimensionally ordered macroporous inverse opal TiO2 nanocomposites (3DOM-TiO2 ). At first and by solving a three dimension Schr?dinger equation we calculated the dependence of charge carriers energies on the size of nanoparticles. Then we investigated the variation of the excitonic energy of BiOV4/3DOM-TiO2, ZnO/3DOM-TiO2 and BiOV4/3DOM-ZnO as function of the radius of these nanostructures into taken account the effects of dielectric and coulomb interaction between charge carriers. We showed that the radiative recombination lifetime is enhanced with decreasing BiVO4 and ZnO quantum dots (QDs) size. It was found that as the size of the dot is reduced the confinement of charge carriers and the optical gap are increased. The optical gap of the ZnO/3DOM-TiO2 is larger than both BiOV4/3DOM-TiO2 and BiOV4/3DOM-ZnO especially for small radius. It was also found that radiative life time in the BiOV4/3DOM-TiO2, ZnO/3DOM-TiO2 and BiOV4/3DOM-ZnO increased by increasing the radius of these nanostructures. In addition, we have also showed that, the radiative lifetime in the ZnO/3DOM-TiO2 nanostructure is less than both BiOV4/3DOM-TiO2 and BiOV4/3DOM-ZnO nanostructures. Finally, we have studied and discussed the Auger process in BiOV4/3DOM-TiO2, ZnO/3DOM-TiO2 and BiOV4/3DOM-ZnO nanostructures. At first, we have showed that the auger process is important when the radiuses of nanostructures are less than 2nm. Then we have also showed that this process is more important for ZnO/3DOM-TiO2 compared to the other nanostructures.
关键词： Photocatalysts,radiative lifetime,Auger recombination lifetime,nanocomposites
更新于2025-09-23 15:23:52
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Negative charge enhancement of near-surface nitrogen vacancy centers by multicolor excitation
摘要： Nitrogen vacancy (NV) centers in diamond have been identified over the past few years as promising systems for a variety of applications, ranging from quantum information science to magnetic sensing. This relies on the unique optical and spin properties of the negatively charged NV. Many of these applications require shallow NV centers, i.e., NVs that are close (a few nm) to the diamond surface. In recent years there has been increasing interest in understanding the spin and charge dynamics of NV centers under various illumination conditions, specifically under infrared (IR) excitation, which has been demonstrated to have significant impact on the NV centers’ emission and charge state. Nevertheless, a full understanding of all experimental data is still lacking, with further complications arising from potential differences between the photodynamics of bulk and shallow NVs. Here we suggest a generalized quantitative model for NV center spin- and charge-state dynamics under both green and IR excitation. We experimentally extract the relevant transition rates, providing a comprehensive model which reconciles all existing experimental results in the literature, except for highly nonlinear regimes. Moreover, we identify key differences between the photodynamics of bulk and shallow NVs, and use them to significantly enhance the initialization fidelity of shallow NVs to the useful negatively charged state.
关键词： nitrogen vacancy centers,recombination,shallow NVs,bulk NVs,photodynamics,green excitation,ionization,charge state,IR excitation,diamond
更新于2025-09-23 15:23:52
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Light-induced EPR study of spin-assisted charge transport in PFOT:PC61BM composite
摘要： Magnetic resonance, relaxation and dynamic parameters of polaron spins and methanfullerene radical anions, initiated by the infrared-visible-ultraviolet photons in bulk heterojunctions of the composite formed by narrow-band poly[(9,9-dioctylfluorenyl-2.7-diyl)-co-(bithiophene)] (PFOT, F8T2) copolymer and [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) globules were investigated by the direct Light-Induced Electron Paramagnetic Resonance (LEPR) spectroscopy. It was shown that some of the polarons are captured by spin traps formed in the copolymer matrix due to its disordering. The number, spatial distribution and energy depth of such traps depend on the structure and morphology of composite. It is shown that the main parameters of both charge carriers are determined by the exchange interaction of the spin ensembles, as well as the energy of the photons. The formation of spin traps in the copolymer matrix and the exchange interaction between different spin packets cause the extreme sensitivity of the composite's magnetic resonance and electronic parameters to the number and energy of the initiating photons. The predominant photoinitiation of localized polarons in the copolymer matrix was demonstrated. This process is substantially accelerated when the composite is illuminated by photons with the energy lying near 1.8 and 2.7 eV. The recombination of both charge carriers can be described in terms of a bimolecular process of the second order. It was found that the contributions of polarons and methanofullerene radical anions to the effective paramagnetic susceptibility increase substantially near the photon energy of 2.6 and 2.1 eV due to the exchange interaction of these charge carriers. It is shown that the mobility of polarons varies monotonically throughout all the photon energy range, whereas the librational spin dynamics of the methanofullerene globules is substantially accelerated near the photon energy of 2.0 and 2.7 eV.
关键词： Polymer nanocomposites,Spin recombination,Transport properties,Spin interaction,Polaron,Light-induced EPR
更新于2025-09-23 15:23:52