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High quality silicon: Colloidal quantum dot heterojunction based infrared photodetector
摘要： The integration of silicon (Si) and nanomaterials with infrared light harvesting capability is a promising approach to fabricate large area infrared light detecting arrays. However, the construction of a high quality junction between Si and small bandgap colloidal quantum dots (CQDs) remains a challenge, which limited their photodetecting performance in the short wavelength infrared region (1.4 lm–3 lm). Herein, a layer of solution processed ZnO nanoparticles was inserted between silicon and CQDs to passivate the surface dangling bond of silicon. This signi?cantly reduces the carrier recombination between Si and CQDs. Meanwhile, the formation of the Si:CQD heterojunction structure enables effective carrier extraction. As a result, the photodetector shows the detecting range to the short wavelength infrared region (0.8 eV) and achieves a standard detectivity of 4.08 (cid:2) 1011 Jones at a bias of (cid:3)0.25 V at room temperature.
关键词： colloidal quantum dot,heterojunction,infrared photodetector,silicon
更新于2025-09-23 15:19:57
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Long carrier lifetime in faceted PbS quantum dot superlattice fabricated by sedimentation method
摘要： We fabricated colloidal quantum dot (QD) superlattice films and investigated their primal optical properties. The films were prepared by depositing faceted PbS QDs on pyramidal-microhole-array template and flat substrate in solution. The red shift in the quantum state emission of QDs was observed in photoluminescence spectra after film formation, which suggested the weakened quantum confinement of carriers in intermediate bands. Emission decay curves at the excited states in the QD superlattice film were double exponential. The longer lifetime was several tens of nanoseconds and attributed to the carrier delocalization in the intermediate bands. The emission lifetime of the QD film prepared on the template was found to be more than twice as long as that on the flat substrate, which suggested that the template helped to form large area QD superlattice.
关键词： sedimentation method,colloidal quantum dot,PbS,superlattice,carrier lifetime
更新于2025-09-23 15:19:57
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Collective topo-epitaxy in the self-assembly of a 3D quantum dot superlattice
摘要： Epitaxially fused colloidal quantum dot (QD) superlattices (epi-SLs) may enable a new class of semiconductors that combine the size-tunable photophysics of QDs with bulk-like electronic performance, but progress is hindered by a poor understanding of epi-SL formation and surface chemistry. Here we use X-ray scattering and correlative electron imaging and diffraction of individual SL grains to determine the formation mechanism of three-dimensional PbSe QD epi-SL films. We show that the epi-SL forms from a rhombohedrally distorted body centred cubic parent SL via a phase transition in which the QDs translate with minimal rotation (~10°) and epitaxially fuse across their {100} facets in three dimensions. This collective epitaxial transformation is atomically topotactic across the 103–105 QDs in each SL grain. Infilling the epi-SLs with alumina by atomic layer deposition greatly changes their electrical properties without affecting the superlattice structure. Our work establishes the formation mechanism of three-dimensional QD epi-SLs and illustrates the critical importance of surface chemistry to charge transport in these materials.
关键词： superlattice,atomic layer deposition,topotaxy,PbSe,colloidal quantum dot,epitaxial fusion
更新于2025-09-19 17:13:59
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Plasmonic Effects of Dual-Metal Nanoparticle Layers for High-Performance Quantum Dot Solar Cells
摘要： To improve quantum dot solar cell performance, it is crucial to make efficient use of the available incident sunlight to ensure that the absorption is maximized. The ability of metal nanoparticles to concentrate incident sunlight via plasmon resonance can enhance the overall absorption of photovoltaic cells due to the strong confinement that results from near-field coupling or far-field scattering plasmonic effects. Therefore, to simultaneously and synergistically utilize both plasmonic effects, the placement of different plasmonic nanostructures at the appropriate locations in the device structure is also critical. Here, we introduce two different plasmonic nanoparticles, Au and Ag, to a colloidal PbS quantum dot heterojunction at the top and bottom interface of the electrodes for further improvement of the absorption in the visible and near-infrared spectral regions. The Ag nanoparticles exhibit strong scattering whereas the Au nanoparticles exhibit an intense optical effect in the wavelength region where the absorption of light of the PbS quantum dot is strongest. It is found that these dual-plasmon layers provide significantly improved short-circuit current and power conversion efficiency without any form of trade-off in terms of the fill factor and open-circuit voltage, which may result from the indirect contact between the plasmonic nanoparticles and colloidal quantum dot films.
关键词： Quantum dot solar cell,Plasmonic effect,Near-field oscillation,Colloidal quantum dot,Light scattering
更新于2025-09-16 10:30:52
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Electronic coupling in colloidal quantum dot molecules; the case of CdSe/CdS core/shell homodimers
摘要： Coupled colloidal quantum dot molecules composed of two fused CdSe/CdS core/shell sphere monomers were recently presented. Upon fusion, the potential energy landscape changes into two quantum dots separated by a pretuned potential barrier with energetics dictated by the conduction and valence band offsets of the core/shell semiconductors and the width controlled by the shell thickness and the fusion reaction conditions. In close proximity of the two nanocrystals, orbital hybridization occurs, forming bonding and antibonding states in analogy to the hydrogen molecule. In this study, we examine theoretically the electronic and optical signatures of such a quantum dot dimer compared to its monomer core/shell building-blocks. We examine the effects of different core sizes, barrier widths, different band offsets, and neck sizes at the interface of the fused facets on the system wave-functions and energetics. Due to the higher effective mass of the hole and the large valence band offset, the hole still essentially resides in either of the cores, breaking the symmetry of the potential for the electron as well. We found that the dimer signature is well expressed in a red shift of the band gap both in absorption and emission, in slower radiative lifetimes and in an absorption cross section which is significantly enhanced relative to the monomers at energies above the shell absorption onset, while remains essentially at the same level near the band-edge. This study provides essential guidance to predesign of coupled quantum dot molecules with specific attributes which can be utilized for various new opto-electronic applications.
关键词： optical signatures,CdSe/CdS core/shell,electronic coupling,colloidal quantum dot molecules,quantum dot dimer
更新于2025-09-12 10:27:22
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Pressure-enhanced electronic coupling of highly passivated quantum dot films to improve photovoltaic performance
摘要： PbS colloidal quantum dot solar cells (CQDSCs) have recently achieved remarkable performance enhancement due to the development of the phase-transfer ligand exchange (PTLE) method. However, the lack of compact packing of the PTLE-passivated CQDs impairs the interdot electronic coupling and thereby severely restricts further improvement in performance. To address this electronic coupling issue, we report a simple yet effective process of external pressure (0–2 MPa). We ?nd that the interdot distance is reduced after the application of the pressure. Both optical and electrical measurements clearly demonstrate that the distance reduction can effectively strengthen the interdot electronic coupling, thus promoting the carrier transport of the CQD layer. However, too much pressure (>2 MPa) could accelerate the detrimental carrier recombination processes of CQDSCs. Accordingly, by optimizing the carrier transport and recombination processes, we achieve the maximum power conversion ef?ciency of 8.2% with a moderate pressure of 1.5 MPa, which is 25.5% higher than the solar cell without the external pressure. This effective strategy of external pressure could also be applied to other CQD-based optoelectronic devices to realize a better device performance.
关键词： external pressure,PbS colloidal quantum dot solar cells,phase-transfer ligand exchange,quantum dot films,Pressure-enhanced electronic coupling,photovoltaic performance
更新于2025-09-12 10:27:22
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Toward Broadband Imaging: Surface Engineered PbS Quantum Dot/Perovskite Composite Integrated Ultrasensitive Photodetectors
摘要： PbS colloidal quantum dots (CQDs) passivated by thiocyanate anion (SCN-) are developed to combine with perovskite (CH3NH3PbI3) as building blocks for UV-vis-NIR broadband photodetectors. Both high electrical conductivity and appropriate energy level alignment are obtained by the in situ ligand exchange with SCN-. The PbS-SCN/CH3NH3PbI3 composite photodetectors are sensitive to a broad wavelength range covering the UV-vis-NIR region (365-1550 nm), possessing an excellent responsivity of 255 AW-1 at 365 nm and 1.58 AW-1 at 940 nm, remarkably high detectivity of 4.9×1013 Jones at 365 nm and 3.0×1011 Jones at 940 nm, and a fast response time ≤ 42 ms. Furthermore, a 10×10 photodetector array is fabricated and integrated, which constitutes a high-performance broadband image sensor. Our approach paves a way for the development of highly sensitive broadband photodetectors/imagers that can be easily integrated.
关键词： PbS colloidal quantum dot,surface engineering,perovskite,broadband imaging,photodetectors
更新于2025-09-12 10:27:22
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Toward Scalable PbS Quantum Dot Solar Cells Using a Tailored Polymeric Hole Conductor
摘要： Colloidal quantum dot (CQD) solar cells processed from pre-exchanged lead sulfide (PbS) inks have received great attention in the development of scalable and stable photovoltaic devices. However, the current hole-transporting material (HTM) 1,2-ethanedithiol-treated PbS (PbS-EDT) CQDs have several drawbacks in terms of commercialization, including the need for oxidation and multilayer fabrication. Conjugated polymers are an alternative HTM with adjustable properties. Here we propose a series of conjugated polymers (PBDB-T, PBDB-T(Si), PBDB-T(S), PBDB-T(F)) for PbS CQD solar cells as HTMs. Through polymer side-chain engineering, we optimize the model polymer PBDB-T to tune the energy levels, increase hole mobility, improve solid-state ordering, and increase free carrier density. CQD solar cells based on modified polymer PBDB-T(F) exhibit a best power conversion efficiency (PCE) of 11.2%, which outperforms the devices based on conventional PbS-EDT HTM (10.6%) and is currently the highest PCE for PbS solar cells based on organic HTMs.
关键词： conjugated polymers,PbS,hole-transporting material,Colloidal quantum dot,power conversion efficiency,solar cells
更新于2025-09-12 10:27:22
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Efficiency Limit of Colloidal Quantum Dot Solar Cells: Effect of Optical Interference on Active Layer Absorption
摘要： Recently, colloidal quantum dot (CQD) solar cells have drawn intense attention because of their accessibility in low-energy solar photons with a facile tunability in electrical properties and their promising feature to go beyond the classic Shockley?Queisser limit of solar cells. Currently, state-of-the-art performance lead sulfide CQD thin-film-based solar cells have a PCE of approximately 12% with large room for improvement. To overcome current limitations on efficiency enhancement in CQD thin-film solar cells, the active layer thickness must increase first by improving carrier transport and formation of band bending to improve collection of carriers. We must note, however, in this heterojunction architecture, estimated optimal active layer thickness has to be revisited considering the interference effect. Specifically, the large refractive index difference between the PbS CQD layer and the ZnO layers account for a significant Fresnel reflection and optical interference in PbS CQD solar cells. This interference effect on high-performing PbS CQD solar cells may not only reduce the effective light absorption but also lead to underestimating the optimal active layer thickness.
关键词： colloidal quantum dot solar cells,optical interference,efficiency limit,active layer absorption
更新于2025-09-12 10:27:22
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Emission behaviors of colloidal quantum dots linked onto synthesized metal nanoparticles
摘要： Emission Behaviors of Colloidal Quantum Dots Linked onto Synthesized Metal Nanoparticles. With two different residual surfactants, four different metal nanoparticles (NPs), including two Au NPs and two Ag NPs are synthesized for linking with red-emitting CdZnSeS/ZnS colloidal quantum dots (QDs) to enhance QD emission efficiency. Those metal NPs are first connected with amino polyethylene glycol thiol of different molecular weights to avoid aggregation and make them positively charged. They can attract negatively charged QDs for inducing surface plasmon (SP) coupling such that either QD absorption or emission and hence overall color conversion efficiency can be enhanced. The enhancement of QD emission efficiency is evaluated through the comparison of time-resolved photoluminescence behaviors under different QD linkage conditions. Such results are confirmed by the measurement of the emission quantum efficiency of QD. It is found that by linking QDs onto Ag NPs, the QD emission efficiency is more enhanced, when compared with Au NPs. Also, depending on the synthesis process, the residual surfactant of citrate leads to a relatively larger increment in QD emission efficiency, when compared to the surfactant of cetrimonium chloride. A more enhanced QD emission efficiency is caused by a higher QD linkage capability and a stronger SP coupling effect.
关键词： colloidal quantum dot,emission efficiency,surface plasmon coupling,synthesized metal nanoparticle
更新于2025-09-11 14:15:04