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Correlation between the open-circuit voltage and recombination loss at metal-silicon interfaces of crystalline silicon solar cells
摘要： For screen-printed silicon solar cells, optimization of the contact characteristics between the front metal electrode and silicon is very significant for realizing high efficiency. As technology advances, the solar cell efficiency has been steadily increased. Especially, as surface recombination becomes more important in high efficiency solar cells, understanding and controlling recombination in the metal contact area are necessary. Recombination at the metal-silicon interface is a major cause of the drop in the open-circuit voltage (Voc) of a solar cell. Thus far, the study of electrodes in silicon solar cells has been largely aimed at reducing the series resistance, and few studies on recombination due to electrodes have been performed. Quantitatively evaluating the recombination in electrodes to assess the effect on the efficiency is expected to become more important in the near future. In this paper, the contact characteristics of a screen-printed silver electrode and silicon interface were analyzed using saturation current density (Jo) measurements according to the surface doping concentration and firing temperature. The effects of the contact characteristics on Voc and recombination were also investigated. Experimental results showed that Jo.pass decreased with decreasing surface doping concentration and Jo.metal increased with increasing surface doping concentration and firing temperature. For quantitative analysis of Jo.metal, the size and distribution of Ag crystallites were observed using SEM and TEM, and the Ag concentration was analyzed by ICP-OES measurements. The larger Jo.metal was, the higher the Ag crystallite concentration, indicating that the Ag crystallites under the electrode increased Jo.metal. The effect of Jo.metal on the electrical characteristics of the solar cell was analyzed by calculating the change in the surface recombination velocity and the decreased width of Voc. Through this study, the recombination in the metallized area, which is expected to become increasingly important, and particularly the effects of the doping profile of the emitter region and silver crystallites on the surface recombination were quantitatively assessed. The amount of silver crystallites on the silicon wafer was quantitatively analyzed.
关键词： Screen-printed silicon solar cells,Saturation current density,Open-circuit voltage,Ag crystallites,Recombination loss,Metal-silicon interface
更新于2025-09-23 15:19:57
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The role of self-trapped excitons in polaronic recombination processes in lithium niobate
摘要： Transient absorption and photoluminescence are experimentally investigated in the polaronic reference system lithium niobate, LiNbO3 (LN), with the aim to refine the microscopic model of small polaron dynamics in materials with strong electron-phonon coupling. As a unique feature, our study is performed by using two different spectroscopic methods, in crystals with dopants enhancing photorefraction or damage resistance, and over a broad temperature range from 15?400 K. Although being self-consistent for particular experimental conditions, the hitherto used microscopic polaronic models reveal inconsistencies when applied to this larger data set. We show that comprehensive modeling is unlocked by the inclusion of an additional type of polaronic state with the following characteristics: (i) strongly temperature- and dopant-dependent relaxation times, (ii) an absorption feature in the blue-green spectral range, and (iii) a Kohlrausch-Williams-Watts decay shape with a temperature-dependent stretching factor β(T ) showing a behavior contrary to that of small, strong-coupling polarons. The hypothesis of self-trapped excitons (STEs, i.e., bound electron-hole pairs strongly coupled to Nb5+ and O2? within a niobium-oxygen octahedron) and their pinning on defects as the microscopic origin of these characteristics is supported by a spectroscopic linkage of photoluminescence at low (15 K) and elevated (300 K) temperatures and explains the long-lifetime components in transient absorption as due to pinned STEs.
关键词： self-trapped excitons,lithium niobate,photoluminescence,transient absorption,polaronic recombination
更新于2025-09-23 15:19:57
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[IEEE 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Austin, TX, USA (2018.9.24-2018.9.26)] 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Nonequilibrium Green’s function method: Büttiker probes for carrier generation and recombination
摘要： The non-equilibrium Green function (NEGF) method is capable of nanodevice performance predictions including coherent and incoherent effects. To treat incoherent scattering, carrier generation and recombination is computationally very expensive. In this work, the numerically efficient B¨uttiker-probe model is expanded to cover recombination and generation effects in addition to various incoherent scattering processes. The capability of the new method to predict nanodevices is exemplified with quantum well III-N light-emitting diodes and anti-ambipolar 2D material heterojunctions.
关键词： B¨uttiker-probe model,non-equilibrium Green function,carrier generation,nanodevices,recombination
更新于2025-09-23 15:19:57
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Biexciton Auger recombination in mono-dispersed, quantum-confined CsPbBr3 perovskite nanocrystals obeys universal volume-scaling
摘要： Auger recombination has been a long-standing obstacle to many prospective applications of colloidal quantum dots (QDs) ranging from lasing, light-emitting diodes to bio-labeling. As such, understanding the physical underpinnings and scaling laws for Auger recombination is essential to these applications. Previous studies of biexciton Auger recombination in various QDs established a universal scaling of biexciton lifetime (τXX) with QD volume (V ): τXX = γV. However, recent measurements on perovskite nanocrystals (NCs), an emerging class of enablers for light harvesting and emitting applications, showed significant deviations from this universal scaling law, likely because the measured NCs are weakly-confined and also have relatively broad size-distributions. Here we study biexciton Auger recombination in mono-dispersed (size distributions within 1.7%–9.0%), quantum-confined CsPbBr3 NCs (with confinement energy up to 410 meV) synthesized using a latest approach based on thermodynamic equilibrium control. Our measurements clearly reproduce the volume-scaling of τXX in confined CsPbBr3 QDs. However, the scaling factor γ (0.085 ± 0.001 ps/nm3) is one order of magnitude lower than that reported for CdSe and PbSe QDs (1.00 ± 0.05 ps/nm3), suggesting unique mechanisms enhancing Auger recombination rate in perovskite NCs.
关键词： biexciton,Auger recombination,perovskite nanocrystals,ultrafast spectroscopy,volume-scaling
更新于2025-09-23 15:19:57
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Influence of morphology on the blinking mechanisms and the excitonic fine structure of single colloidal nanoplatelets
摘要： Colloidal semiconductor nanoplatelets with a similar electronic structure as quantum wells have recently emerged as exciting materials for optoelectronic applications. Here we investigate how morphology affects important photoluminescence properties of single CdSe and core/shell CdSe/CdZnS nanoplatelets. By analyzing photoluminescence intensity-lifetime correlation and second-order photon correlation results, we demonstrate that, irrespective of the morphology, Auger recombination plays only a minor role in dictating the blinking behavior of the nanoplatelets. We find that a rough shell induces additional non-radiative channels presumably related to defects or traps of an imperfect shell. Furthermore, polarization-resolved spectroscopy analysis reveals exciton fine-structure splitting of the order of several tens of meV in rough-shell nanoplatelets at room temperature, which is attributed to exciton localization and is substantiated by theoretical calculations taking into account the nanoplatelet shape and electron–hole exchange interaction.
关键词： exciton fine structure,photoluminescence,nanoplatelets,blinking,Auger recombination
更新于2025-09-19 17:15:36
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Carrier reduction studies of type-II superlattice materials for very long wavelength infrared sensing
摘要： There are continuing efforts to develop type-II superlattice (SL) materials for very long wavelength infrared (VLWIR) detector applications. However, the SLs have high residual electron background doping densities that depend on SL growth conditions, which lead to shorter minority carrier lifetime and lower performance parameters than theoretically predicted. In this study, the authors compare the technical advantages of using InAs/GaInSb over InAs/GaSb SL with respect to reducing the electron doping levels. Our temperature-dependent electrical transport measurements show that the InAs/GaInSb SL design has a lower electron density than the InAs/GaSb SL with the same bandgap and have electron densities (mobilities) on the order of the mid 1011 cm?2 (25 000 cm2/V s). Since small period InAs/GaInSb SLs also produce greater Auger recombination suppression for a given VLWIR gap than the large period InAs/GaSb SL, the InAs/GaInSb SL appears to be a better candidate for long lifetime IR materials for future very long wavelength infrared devices.
关键词： very long wavelength infrared,mobility,InAs/GaSb,Auger recombination,InAs/GaInSb,type-II superlattice,carrier reduction,electron doping
更新于2025-09-19 17:15:36
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Reducing the surface recombination during light-driven water oxidation by core-shell BiVO4@Ni:FeOOH
摘要： The photocurrent of BiVO4 is limited by surface recombination not surface catalysis, which is currently reported as the main restrict factor for high efficiency photo-electrochemical (PEC) water splitting. To solve this problem, an ultrathin Ni:FeOOH (~ 8 nm) modified nanoporous BiVO4 photoanode (BiVO4@Ni:FeOOH) was constructed with core-shell structure for PEC water oxidation. Attributed to the p-n hetero-junction formed between BiVO4 and Ni:FeOOH, the photocurrent density of BiVO4@Ni:FeOOH increased by a factor of 11 (2.86 mA cm-2 at 1.23 V vs. RHE), together with ~ 180 mV negative shift of onset potential under AM 1.5 G irradiation (100 mW cm-2) in comparison to the pristine BiVO4. More importantly, detailed insight into the fate of the photo-generated charge carriers at the surface is investigated. Intensity modulated photocurrent spectroscopy (IMPS) is used to investigate the surface carrier dynamics of BiVO4 and BiVO4@Ni:FeOOH. IMPS results and hole scavenger measurement (HSM) certify the main role of Ni:FeOOH is to improve surface recombination by largely decreasing the surface recombination rate constant (krec), not surface catalysis. This work demonstrates Ni:FeOOH can facilitate local surface kinetics and reduce recombination rates as well and be used in other photoelectrodes especially the photoanodes with surface defects for PEC water splitting.
关键词： Core-shell,intensity modulated photocurrent spectroscopy,p-n heterojunction,surface recombination
更新于2025-09-19 17:15:36
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Indolo[3,2- <i>b</i> ]indole donor-based D–π–A dyes for DSCs: investigating the role of π-spacers towards recombination
摘要： Dye solar cells (DSCs) are gaining increasing interest since the recent realization of their high-performance in low/indoor light environments. Fused conjugated metal-free organic dyes have become a prominent class of dyes used in DSC in recent times by virtue of their better backbone rigidity, efficient charge transport properties, and the opportunity they provide for further structural modifications. Herein, we report the synthesis and characterization of three metal-free D–π–A organic dyes employing indolo[3,2-b]indole as the donor unit. The optical, electrochemical and photovoltaic properties have been analyzed in detail as a function of π-spacers, namely, benzene (IID-1), thiophene (IID-2) and furan (IID-3). Eventually, the best performance was demonstrated by the dye bearing benzene as the π-spacer. The role of recombination in determining the photovoltaic performance as a function of the nature of π-spacers was explored in detail, using various perturbation techniques on the fabricated devices, and compared with the results obtained from molecular orbital calculations.
关键词： π-spacers,Recombination,2-b]indole,Dye solar cells,Indolo[3,Photovoltaic performance,D–π–A dyes
更新于2025-09-19 17:15:36
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-doped yttrium orthophosphate nanoparticles tailored by co-precipitation route
摘要： Sm3+ doped yttrium orthophosphate nanoparticles with porous structure was synthesized via simple co-precipitation method. The structure, the morphology and the elemental composition of the tailored nanoparticles were investigated using transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDAX). Under the influence of trisodium citrate, Sm3+ doped YPO4 phosphor with porous structure could be synthesized. Under our reaction conditions, Sm3+ doped YPO4 nanophosphor crystallize in the hexagonal structure, as confirmed by the powder XRD patterns. The formation of porous structure turned out to be an essential step for the peculiar luminescent properties. The porosity undoubtedly enlarges the surface of the semiconductor/air interface, resulting in suppression of the non-radiative recombination channels. The tailored porous yttrium orthophosphate nanoparticles significantly displayed potentiality in the field of optical displays and also demonstrated the applicability in the biological field.
关键词： optical,non-radiative,biological field,porous,recombination channels,crystallize
更新于2025-09-19 17:15:36
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Janus Chromium Dichalcogenides Monolayers with Low Carrier Recombination for Photocatalytic Overall Water-Splitting under Infrared Light
摘要： Photocatalytic overall water-splitting is known as one of most promising methods to alleviate energy crisis. Searching for stable and efficient photocatalysts plays a critical role in this process. Here, we propose a novel class of Janus chromium dichalcogenides (CrXY, X/Y = S, Se, Te) monolayers serving as efficient photocatalysts for overall water-splitting under infrared light irradiation. We reveal that these Janus monolayers harbor an intrinsic dipole, which promotes the spatial separation of photo-generated carriers. More significantly, these systems exhibit suitable band gaps as well as band edge positions, enabling preeminent infrared optical absorption and high carrier mobility. Furthermore, the nonradiative recombination of photoinduced charge carriers in CrXY monolayers are evaluated based on time-domain density functional theory. The obtained long-lived excited carriers (~ 2 ns) are even comparable with that in transition-metal dichalcogenides heterostructures, which benefits for the photocatalytic reaction with high efficiency. Our results provide a new guidance for designing brand new photocatalytic systems with broad optical absorption and low carrier recombination.
关键词： infrared light,first principles calculations,carrier recombination,Janus chromium dichalcogenides,photocatalytic water-splitting
更新于2025-09-19 17:15:36