- 标题
- 摘要
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- 实验方案
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Core/Shell Quantum Dots Solar Cells
摘要： Semiconductor nanocrystals, the so-called quantum dots (QDs), exhibit versatile optical and electrical properties. However, QDs possess high density of surface defects/traps due to the high surface-to-volume ratio, which act as nonradiative carrier recombination centers within the QDs, thereby deteriorating the overall solar cell performance. The surface passivation of QDs through the growth of an outer shell of different materials/compositions called “core/shell QDs” has proven to be an effective approach to reduce the surface defects and confinement potential, which can enable the broadening of the absorption spectrum, accelerate the carrier transfer, and reduce exciton recombination loss. Here, the recent research developments in the tailoring of the structure of core/shell QDs to tune exciton dynamics so as to improve solar cell performance are summarized. The role of band alignment of core and shell materials, core size, shell thickness/compositions, and interface engineering of core/thick shell called “giant” QDs on electron–hole spatial separation, carrier transport, and confinement potential, before and after grafting on the carrier scavengers (semiconductor/electrolyte), is described. Then, the solar cell performance based on core/shell QDs is introduced. Finally, an outlook for the rational design of core/shell QDs is provided, which can further promote the development of high-efficiency and stable QD sensitized solar cells.
关键词： core/shell quantum dots,carrier dynamics,solar cells,interface engineering
更新于2025-09-19 17:13:59
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Modulation Behaviors, Conductivities, and Carrier Dynamics of Single and Multilayer Graphenes
摘要： Time domain and time resolved terahertz studies of single- and multi-layer graphene (SLG and MLG) samples and modulator devices will be presented. A high performance up to 100% of modulators were observed with the devices even at very low voltages. High modulation depth over such a broad spectrum and simple device structure brings significant importance toward application of this type of device in THz and related technologies. In addition, conductivities of SLG and MLG devices were also investigated and a change in behavior was observed as the layer thickness increased. The charge carriers dynamics of the samples with pulp fluence and color was also highly interesting.
关键词： modulator,carrier dynamics,conductivity,terahertz,graphene
更新于2025-09-16 10:30:52
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Ultrafast self-trapping of photoexcited carriers sets the upper limit on antimony trisulfide photovoltaic devices
摘要： Antimony trisulfide (Sb2S3) is considered to be a promising photovoltaic material; however, the performance is yet to be satisfactory. Poor power conversion efficiency and large open circuit voltage loss have been usually ascribed to interface and bulk extrinsic defects. By performing a spectroscopy study on Sb2S3 polycrystalline films and single crystal, we show commonly existed characteristics including redshifted photoluminescence with 0.6 eV Stokes shift, and a few picosecond carrier trapping without saturation at carrier density as high as approximately 1020 cm?3. These features, together with polarized trap emission from Sb2S3 single crystal, strongly suggest that photoexcited carriers in Sb2S3 are intrinsically self-trapped by lattice deformation, instead of by extrinsic defects. The proposed self-trapping explains spectroscopic results and rationalizes the large open circuit voltage loss and near-unity carrier collection efficiency in Sb2S3 thin film solar cells. Self-trapping sets the upper limit on maximum open circuit voltage (approximately 0.8 V) and thus power conversion efficiency (approximately 16 %) for Sb2S3 solar cells.
关键词： Carrier dynamics,Self-trapping,Solar cells,Antimony trisulfide,Photovoltaic material
更新于2025-09-16 10:30:52
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Enhanced terahertz emission bandwidth from photoconductive antenna by manipulating carrier dynamics of semiconducting substrate with embedded plasmonic metasurface
摘要： In this article, we demonstrate a technique to enhance the Terahertz (THz) emission bandwidth from photo-conductive antenna (PCA) based on semiconducting substrates by manipulating the surface carrier dynamics of the semiconductor. Bandwidths in PCAs are limited by the decay of the photogenerated charge carriers, which in case of SI-GaAs is in the orders of 50 picoseconds. We show, with an embedded design of plasmonic meta-surface in the photoconductive gap of a PCA, it is possible to enhance the emission bandwidths by more than 50 percent. This is due to the fact that these nano-structures act as local recombination sites for the photogenerated carriers, effectively reducing the carriers’ lifetime. Additionally, the defect sites reduce the terminal current, thereby reducing the Joule heating in the device. Furthermore, the meta-surface also facilitates higher in-coupling of the exciting infrared light on to the PCA, thereby increasing the optical-to-THz conversion efficiency of the device.
关键词： carrier dynamics,plasmonic metasurface,bandwidth enhancement,photoconductive antenna,Terahertz
更新于2025-09-16 10:30:52
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Individual nanostructure optimization in donor and acceptor phases to achieve efficient quaternary organic solar cells
摘要： Fullerene derivative (PC71BM) and high crystallinity molecule (DR3TBDTT) are employed into PTB7-Th:FOIC based organic solar cells (OSCs) to cooperate an individual nanostructure optimized quaternary blend. PC71BM functions as molecular adjuster and phase modifier promoting FOIC forming “head-to-head” molecular packing and neutralizing the excessive FOIC crystallites. A multi-scale modified morphology is present thanks to the mixture of FOIC and PC71BM while DR3TBDTT disperses into PTB7-Th matrix to reinforce donor’s crystallinity and enhance domain purity. Morphology characterization highlights the importance of individually optimizated nanostructures for donor and acceptor, which contributes to efficient hole and electron transport toward improved carrier mobilities and suppressed non-geminated recombination. Therefore, a power conversion efficiency of 13.51% is realized for a quaternary device which is 16% higher than the binary device (PTB7-Th:FOIC). This work demonstrates that utilizing quaternary strategy for simultaneous optimization of donor and acceptor phases is a feasible way to realize high efficient OSCs.
关键词： carrier dynamics,quaternary organic solar cells,hierarchical morphology optimization,fullerene,non-fullerene
更新于2025-09-16 10:30:52
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Fluorine Tuning of Morphology, Energy Loss, and Carrier Dynamics in Perylenediimide Polymer Solar Cells
摘要： We investigate backbone fluorination effects in bulk-heterojunction (BHJ) polymer solar cells (PSCs) with the fluorine-poor PBDTT-FTTE and fluorine-rich PBDTTF-FTTE donor polymers, paired with the perylenediimide (PDI) 3D “propeller acceptor” Ph(PDI)3. The PBDTTF-FTTE:Ph(PDI)3 devices exhibit a > 50 % power conversion efficiency (PCE, up to 9.1%) increase versus PBDTT-FTTE:Ph(PDI)3. This enhancement reflects structurally optimized phase separation due to templating effects, affording reduced energy loss, higher electron mobility, greater free charge lifetimes and yields, and lower bimolecular recombination, as quantified by UPS, AFM, TEM, GIWAXS, SCLC, light intensity dependence measurements, and fs/ns transient absorption (TA) spectroscopy. In PBDTTF-FTTE, the DFT-computed dipole orientations of the ground and excitonic states is nearly antiparallel, explaining the longer free charge lifetimes, minimized recombination, and lowered exciton binding energy. The PBDTTF-FTTE:Ph(PDI)3 performance enhancement vs. that of the fluorine-poor PBDTT-FTTE:Ph(PDI)3 analogue as well as the overall PSC performance exceeds that of the corresponding PC71BM- and ITIC-Th-based cells.
关键词： Perylenediimide,Energy loss,Fluorine tuning,Carrier dynamics,Morphology,Polymer solar cells
更新于2025-09-16 10:30:52
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Lateral carrier transfer for high density InGaAs/GaAs surface quantum dots
摘要： In(Ga)As surface quantum dots (SQDs) are promising candidates for surface-sensitive detection applications. As such, studies of the carrier dynamics are indispensable when attempting to understand both the physics and the device performances based on such SQD structures. Here, lateral carrier transfer among neighboring quantum dots (QDs) has been investigated through spectroscopic measurements for high density InGaAs/GaAs SQDs in a hybrid nanostructure with similar buried QDs (BQDs). Photoluminescence (PL) and temporal-resolved PL (TRPL) spectra demonstrate that the SQDs exhibit intra-layer exciton transfer and also strong carrier transfer to the surface states at 10 K. This imparts different optical characteristics to the SQDs with regards to the band filling and emission-energy-dependent carrier lifetime. In addition, PL excitation (PLE) spectra reveal a wetting layer absorption feature for the SQDs, which provides a channel for thermally activated carriers to transfer among the SQDs and to ultimately escape from the SQD layer. These investigations enrich our understanding of carrier dynamics for InGaAs SQDs, which may help to develop novel surface sensitive sensors.
关键词： Surface quantum dots,lateral carrier transfer.,carrier dynamics,photoluminescence
更新于2025-09-12 10:27:22
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Hot carrier dynamics in a dispersionless plasmonic system
摘要： Hot carrier dynamics in a broadband, dispersionless, plasmonic structure are studied using pump-probe measurements with 45 fs time resolution. The results obtained by simultaneous measurement of differential transmittance and reflectance show the influence of pump generated carriers on the probe generated plasmons. The dependence of decay time on the pump fluence is linear for the interband and intraband carrier excitation near the L-symmetry point in gold. However, 1.908 eV pump excitation, which allows both interband transition at the X-symmetry point and intraband excitation at the L-symmetry point, shows quadratic dependence of decay time on the pump fluence. Degenerate pump-probe measurements at 1.55 eV, which allow L-valley intraband excitations, highlight the difference in surface (reflection) and the bulk (transmission) mechanisms. Hot carrier relaxation time is in the 1–3 ps range for different excitation energies. Rise time, governed by the plasmon to hot carrier conversion and electron-electron scattering processes, is about 200 ± 35 fs for the hot carrier and hot plasmon excitation cases that increased to about 485 ± 35 fs when the pump is resonant with the interband transition at the X-symmetry point. Results show that the hot carrier dynamics are governed by the bulk metal band structure. The dipole matrix element for each of the transitions is estimated by density matrix calculations.
关键词： pump-probe measurements,gold band structure,differential transmittance,reflectance,plasmonic system,hot carrier dynamics
更新于2025-09-12 10:27:22
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Tailored interfacial crystal facets for efficient CH3NH3PbI3 perovskite solar cells
摘要： Interface engineering is generally requisite for highly efficient perovskite solar cells (PSCs). However, the current interface engineering methods inevitably introduce extra modifier layers into PSCs, which not only complex the configurations and fabrication procedures, but also increase the production cost of PSCs. Herein, we propose an interface engineering strategy for PSCs by controlling the nature of Lead halide perovskite films, and specifically their interfacial grain facets. In detail, a solution-mediated secondary growth (SSG) technology is demonstrated to tailor interfacial grain facets in CH3NH3PbI3 PSC. The precise tailoring ability of interfacial grain facets is achieved by controlling SSG temperature. When it is optimized to 60 °C, interfacial grains of CH3NH3PbI3 film can be fully transform from dodecahedral-shaped ones enclosed by (100) and (112) facets to the cubic-shaped ones enclosed by (110) and (002) facets, while maintaining the film’s crystalline phase and composition. More importantly, such transitions are accompanied by significantly improved average PCE from 16.51±0.64% to 18.40±0.67% for the optimized CH3NH3PbI3 PSCs, benefiting from the greatly suppressed recombination and enhanced extraction of carriers.
关键词： carrier dynamics,interface engineering,perovskite solar cells,crystal facets,solution-mediated secondary growth
更新于2025-09-12 10:27:22
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Plasmonic Hot Hole Transfer in Gold Nanoparticle-decorated Transition Metal Dichalcogenide Nanosheets
摘要： This work studies photogenerated carrier dynamics in gold nanoparticle (AuNP)-decorated mono- to few-layer transition metal dichalcogenide (TMD) nanosheets using transient absorption spectroscopy (TA). TA unveiled the presence of a long-lived photo-induced absorption (PIA) feature in both MoSe2 and WSe2 decorated with covalently bound AuNPs. This long-lived PIA feature emerges only from direct Au interband excitation in AuNP-decorated MoSe2 and WSe2; it does not manifest from intraband excitation nor in AuNP-decorated MoS2 or WS2. Based on x-ray/ultraviolet photoelectron spectroscopy and previous theoretical studies, it is proposed that this PIA signature arises from hot hole transfer from the AuNP to the adjacent TMD, producing a charge-separated state. This suggests charge separation at the metal-semiconductor interface may be used to extend the lifetime of interband excitation generated hot holes. This development could represent an important advance in harnessing plasmonic dissipation pathways to generate long-lived carriers suited for solar-driven light harvesting and catalysis.
关键词： molybdenum diselenide,hot carriers,transient absorption,carrier dynamics,intraband,interband transitions,ultrafast spectroscopy
更新于2025-09-12 10:27:22