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A Chemically Orthogonal Hole Transport Layer for Efficient Colloidal Quantum Dot Solar Cells
摘要： Colloidal quantum dots (CQDs) are of interest in light of their solution-processing and bandgap tuning. Advances in the performance of CQD optoelectronic devices require fine control over the properties of each layer in the device materials stack. This is particularly challenging in the present best CQD solar cells, since these employ a p-type hole-transport layer (HTL) implemented using 1,2-ethanedithiol (EDT) ligand exchange on top of the CQD active layer. It is established that the high reactivity of EDT causes a severe chemical modification to the active layer that deteriorates charge extraction. By combining elemental mapping with the spatial charge collection efficiency in CQD solar cells, the key materials interface dominating the subpar performance of prior CQD PV devices is demonstrated. This motivates to develop a chemically orthogonal HTL that consists of malonic-acid-crosslinked CQDs. The new crosslinking strategy preserves the surface chemistry of the active layer beneath, and at the same time provides the needed efficient charge extraction. The new HTL enables a 1.4× increase in charge carrier diffusion length in the active layer; and as a result leads to an improvement in power conversion efficiency to 13.0% compared to EDT standard cells (12.2%).
关键词： hole transport layers,colloidal quantum dots,solar cells,chemical orthogonality,surface ligands
更新于2025-09-23 15:19:57
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Narrowband colloidal quantum dot photodetectors for wavelength measurement applications
摘要： High performance photodetectors based on colloidal quantum dots have been demonstrated in a wide spectral range spanning from the visible to the mid infrared. Quantum dot photodetectors typically show a low-pass type spectral response with a tunable cutoff wavelength. In this paper, we propose a method for the realization of narrowband photodetectors based on the combination of photoconductors and optical filters, both realized with colloidal PbS quantum dots. We demonstrate that an array of such narrowband photodetectors can be effectively employed for the realization of a compact wavemeter operating in the visible and near-infrared spectral range.
关键词： Narrowband photodetectors,Wavelength meter,Colloidal Quantum Dots photodetectors
更新于2025-09-23 15:19:57
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Ligand engineering of colloid quantum dots and their application in all-inorganic tandem solar cells
摘要： How to effectively utilize the energy of the broad spectrum of sunlight is one of the basic problems in the research of tandem solar cells. Due to their size effect, quantum confinement effect and coupling effect, colloidal quantum dots (QDs) exhibit new physical properties that bulk materials don’t possess. CdX (X=Se, S, etc.) and PbX (X=Se, S, etc.) QDs prepared by hot-injection methods have been widely studied in the areas of photovolitaic devices. However, the surfactants surrounding QDs seriously hinder the charge transport of QDs based solar cells. Therefore, how to fabricate high-performance tandem solar cells via ligands engineering has become a major challenge. In this paper, the latest progress of colloidal QDs in the research of all-inorganic tandem solar cells was summarized. Firstly, the improvement of QDs surface ligands and the optimization of ligands engineering were discussed, and the control of the physical properties of QDs films were realized. From the aspects of colloidal QDs, ligand engineering, and solar cell preparation, the future development direction of colloidal QDs solar cells was proposed, providing technical guidances for the preparation of low-cost and high-efficiency nanocrystalline solar cells.
关键词： Tandem solar cell,Colloidal quantum dots,Hot-injection method,Ligand engineering
更新于2025-09-23 15:19:57
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Excess Random Laser Action in Memories for Hybrid Optical/Electric Logic
摘要： To surmount the scalability limitations of the nano-electronics industry, the invention of resistance random access memory (RRAM) has drawn considerable attention in recent years for being a new-era memory. Nevertheless, the data transmission speed of RRAM is confined by virtue of its sequential reading nature. To improve upon this weakness, a hybrid optical/electric memory with ION/IOFF ratio up to 105 and laser-level optical signal is proposed. The device was engineered through an adroit design of integrating a random laser (RL) into the conducting bridge random access memory (CBRAM). According to the electrochemical metallization (ECM) effect of CBRAM, agglomerative silver nanoparticles form in the insulating layer during the ON/OFF switching process, which can serve as scattering centers. By adding CdSe/ZnS quantum dots (QDs) as gain medium, a random laser system is obtained. Due to the quantum confinement effect, the device also features spectral tunable signal feedback by modulating the size of the QDs. In this study, devices with two different sizes of QDs are demonstrated such that a multiple-bits AND gate logic can be achieved. The innovation behind this RL-ECM memory might facilitate a key step toward the development of ultrahigh speed information technology.
关键词： RRAM,AND gate logic,random laser,electrochemical metallization effect,CdSe/ZnS colloidal quantum dots
更新于2025-09-23 15:19:57
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Nonlinear optical properties of colloidal CdSe/ZnS quantum dots in PMMA
摘要： The colloidal CdSe/ZnS quantum dots (QDs) in the PMMA polymer film with different QDs concentrations were fabricated. The influence of QDs concentration and excitation pump energy on nonlinear optical (NLO) properties of PMMA capped CdSe/ZnS QDs was investigated by the Z-scan technique with nanosecond laser pulses in the near-infrared spectral band. A large effective nonlinear absorption coefficient (βeff～?10?13 esu) due to the saturable absorption was observed. It was found that the appropriate concentration could lead to the reinforcement of NLO effect. In addition, the impact of the excitation energy on the nonlinear refractive index n2, real and imaginary parts of the third-order nonlinear optical susceptibility was also performed. This study involving the light–matter interactions in the colloidal quantum dots will benefit potential NLO-based applications of optoelectronics, optical modulation and photonics.
关键词： nanophotonics,semiconductor colloidal quantum dots,impact behavior,Z-scan technique,nonlinear optical (NLO) properties
更新于2025-09-23 15:19:57
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Optimizing Solid-State Ligand Exchange for Colloidal Quantum Dot Optoelectronics: How Much Is Enough?
摘要： Progress in chalcogenide and perovskite CQD optoelectronics has relied in significant part on solid-state ligand exchanges (SSEs): the replacement of initial insulating ligands with shorter conducting linkers on CQD surfaces. Herein we develop a mechanistic model of SSE employing 3-mercaptopropionic acid (MPA) and 1,2-ethanedithiol (EDT) as the linkers. The model suggests that optimal linker concentrations lead to efficient exchange resulting in ca. 200 – 300 exchanged ligands per CQD, a 50% thickness reduction of the initial film, decreased interdot spacing, a 15 nm red-shift in the excitonic absorption peak and a 10x reduction in carrier lifetime. It is a combined effect of these physico-chemical changes that have traditionally made 1% MPA and 10-2% EDT (v:v) the concentrations of choice for efficient CQD optoelectronics.
关键词： Colloidal quantum dots,1,2-ethanedithiol,solid-state ligand exchange,3-mercaptopropionic acid,solar cells
更新于2025-09-23 15:19:57
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Dynamic Ligand Surface Chemistry of Excited PbS Quantum Dots
摘要： The ligand shell around colloidal quantum dots mediates the electron and energy transfer processes that underpin their use in optoelectronic and photocatalytic applications. Here, we show that the surface chemistry of carboxylate anchoring groups of oleate ligands passivating PbS quantum dots undergoes significant changes when the quantum dots are excited to their excitonic states. We directly probe the changes of surface chemistry using time-resolved mid-infrared spectroscopy that records the evolution of the vibrational frequencies of carboxylate groups following excitation of the electronic states. The data reveal a reduction of the Pb?O coordination of carboxylate anchoring groups to lead atoms at the quantum dot surfaces. The dynamic surface chemistry of the ligands may increase their surface mobility in the excited state and enhance the ability of molecular species to penetrate the ligand shell to undergo energy and charge transfer processes that depend sensitively on distance.
关键词： surface chemistry,PbS quantum dots,ligand shell,colloidal quantum dots,time-resolved mid-infrared spectroscopy
更新于2025-09-19 17:13:59
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Ag2ZnSnS4 Nanocrystals Expand the Availability of RoHS Compliant Colloidal Quantum Dots
摘要： The demonstration of the quantum confinement effect in colloidal quantum dots (QDs) has been extensively studied and exploited mainly in Pb and Cd chalcogenide systems. There has been an urgent need recently for the development of non(less)-toxic colloidal QDs to warrant compliance with current safety regulations (Restriction of Hazardous Substances (RoHS) Directive 2002/95/EC). Herein, we report Pb/Cd-free, solution processed luminescent Ag2ZnSnS4 (AZTS) colloidal QDs. We present a selective and controlled amine and thiol-free synthesis of air stable luminescent Ag2ZnSnS4 QDs by hot injection technique. By controlling the reaction conditions we obtain controlled size variation, and demonstrate the quantum confinement effect that is in good agreement with the theoretically calculated values. The bandgap of the AZTS QDs is size-tunable in the near infrared from 740 nm to 850 nm. Finally, we passivate the surface with Zn-oleate, which yields higher quantum yield (QY), longer lifetime and better colloidal stability.
关键词： near infrared,RoHS compliant,Ag2ZnSnS4,colloidal quantum dots,quantum confinement,Zn-oleate passivation
更新于2025-09-19 17:13:59
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PbE (E = S, Se) Colloidal Quantum Dot-Layered 2D Material Hybrid Photodetectors
摘要： Hybrid lead chalcogenide (PbE) (E = S, Se) quantum dot (QD)-layered 2D systems are an emerging class of photodetectors with unique potential to expand the range of current technologies and easily integrate into current complementary metal-oxide-semiconductor (CMOS)-compatible architectures. Herein, we review recent advancements in hybrid PbE QD-layered 2D photodetectors and place them in the context of key findings from studies of charge transport in layered 2D materials and QD films that provide lessons to be applied to the hybrid system. Photodetectors utilizing a range of layered 2D materials including graphene and transition metal dichalcogenides sensitized with PbE QDs in various device architectures are presented. Figures of merit such as responsivity (R) and detectivity (D*) are reviewed for a multitude of devices in order to compare detector performance. Finally, a look to the future considers possible avenues for future device development, including potential new materials and device treatment/fabrication options.
关键词： photodetectors,phosphorene,infrared,PbS,graphene,layered 2D materials,TMDs,colloidal quantum dots,PbSe
更新于2025-09-19 17:13:59
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Environmentally friendly Mn-alloyed core/shell quantum dots for high-efficiency photoelectrochemical cells
摘要： Colloidal quantum dots (QDs)-based photoelectrochemical (PEC) cells are cost-effective devices showing remarkable solar-to-fuel conversion efficiency. However, the extensive use of highly toxic elements (e.g. Pb and Cd) in QD’s synthesis and device fabrication is still a major challenge towards their practical development. Herein, we fabricate a solar-driven PEC cell based on environment-friendly Mn-alloyed CuInS2 (MnCIS)/ZnS core/shell QDs, showing more favorable band alignment, efficient charge transfer, reduced charge recombination as well as lower charge transfer resistance with respect to the control device fabricated using unalloyed CuInS2 (CIS)/ZnS core/shell QDs. An unprecedented photocurrent density of ~5.7 mA/cm2 with excellent stability was obtained in as-fabricated MnCIS/ZnS core/shell QDs-based PEC device when operated under standard one solar irradiation (AM 1.5G, 100 mW/cm2). These results indicate that the transition metal-alloyed environment-friendly core/shell QDs are promising for next-generation solar technologies.
关键词： Colloidal quantum dots,Photoelectrochemical cells,Mn-alloyed CuInS2,ZnS core/shell,Solar-to-fuel conversion
更新于2025-09-19 17:13:59