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Photons and charges from colloidal doped semiconductor quantum dots
摘要： The utility of colloidal semiconductor quantum dots as a source of photons and charge carriers for photonic and photovoltaic applications has created a large field of research focused on tailoring and broadening their functionality beyond what an exciton can provide. One approach towards expanding the range of characteristics of photons and charge carriers from quantum dots is through doping impurity ions (e.g. Mn2+, Cu+, and Yb3+) in the host quantum dots. In addition to the progress in synthesis enabling fine control of the structure of the doped quantum dots, a mechanistic understanding of the underlying processes correlated with the structure has been crucial in revealing the full potential of the doped quantum dots as the source of photons and charge carriers. In this review, we discuss the recent progress made in gaining microscopic understanding of the photophysical pathways that give rise to unique dopant-related luminescence and the generation of energetic hot electrons via exciton-to-hot electron upconversion.
关键词： doping impurity ions,charge carriers,photons,hot electrons,colloidal semiconductor quantum dots,photophysical pathways
更新于2025-09-16 10:30:52
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Tail state limited photocurrent collection of thick photoactive layers in organic solar cells
摘要： We analyse organic solar cells with four different photoactive blends exhibiting differing dependencies of short-circuit current upon photoactive layer thickness. These blends and devices are analysed by transient optoelectronic techniques of carrier kinetics and densities, air photoemission spectroscopy of material energetics, Kelvin probe measurements of work function, Mott-Schottky analyses of apparent doping density and by device modelling. We conclude that, for the device series studied, the photocurrent loss with thick active layers is primarily associated with the accumulation of photo-generated charge carriers in intra-bandgap tail states. This charge accumulation screens the device internal electrical field, preventing efficient charge collection. Purification of one studied donor polymer is observed to reduce tail state distribution and density and increase the maximal photoactive thickness for efficient operation. Our work suggests that selecting organic photoactive layers with a narrow distribution of tail states is a key requirement for the fabrication of efficient, high photocurrent, thick organic solar cells.
关键词： tail states,charge carriers,photoactive blends,organic solar cells,charge collection
更新于2025-09-12 10:27:22
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Visualizing the Impact of Light Soaking on Morphological Domains in an Operational Cesium Lead Halide Perovskite Solar Cell
摘要： The dynamics of photogenerated carriers and mobile ions in an operational cesium lead halide (CsPbI3) perovskite solar cells (PSC) under working conditions are studied using nanoscale resolved photoluminescence (PL) lifetime imaging microscopy. The temporally and spatially resolved PL changes in the perovskite film during and after bias light soaking are dynamically monitored. By analyzing the dynamic variations of PL intensity and PL lifetime of an open-circuited PSC, the impacts of light soaking are revealed by a dynamic model of photogenerated charge carrier and mobile ions. We confirmed the different behavior from morphological domains interiors and domains boundaries during light soaking, which shed light on the engineering of the domain interiors in additions to the commonly considered domain boundary strategies. This work provides a full picture of the photogenerated process in an operating PSC and therefore guides the design and operation of perovskite-based optoelectronic devices.
关键词： charge carriers,perovskite solar cells,mobile ions,light soaking,photoluminescence
更新于2025-09-12 10:27:22
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Composited micropores constructed by amorphous TiO2 and graphene for degrading volatile organic compounds
摘要： The adsorption ability and photoactivity of photocatalysts directly determine the mineralization efficiency of volatile organic compounds. In this study, a 2D–2D microporous structure of amorphous TiO2 nanoparticles and graphene (GR) was constructed to simultaneously enhance the adsorption ability and charge separation efficiency of catalysts. N2 adsorption–desorption, scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction measurements were conducted to investigate the physical properties of the prepared samples. The atmospheric surface photovoltage (SPV) was utilized to study the separation process of the photogenerated charge carriers. Toluene was chosen as the model agent to estimate the adsorption ability and photoactivity of the samples. Results showed that the amorphous TiO2 nanoparticles homogeneously deposited onto the GR surface and hence formed a 2D–2D microporous structure. Although the surface area of the GR–TiO2 compositions increased by only 4–8% relative to that of microporous TiO2 alone, the amount of adsorbed toluene for the GR–TiO2 compositions was 156–193% times higher than that for the microporous TiO2. The SPV result proved that the GR significantly enhanced the intrinsic separation of the photogenerated charge carriers. The contribution of O2 and the GR to the charge separation was dependent on the weight addition ratio of the GR. The GR dominated the charge separation process as its weight addition ratio ≥5%. Given the advantages in adsorption ability and photoactivity, toluene showed mineralization efficiencies for the composite with 5.0 wt% GR of 1.4 and 2.7 folds those of microporous TiO2 and P25, respectively, after 96 min irradiation.
关键词： Charge carriers,Surface photovoltage,Micropore,Mineralization,Adsorption
更新于2025-09-10 09:29:36
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Rational Design of Graphic Carbon Nitride Copolymers by Molecular Doping for Visible-Light-Driven Degradation of Aqueous Sulfamethazine and Hydrogen Evolution
摘要： Carbon nitride is a promising metal-free visible light driven photocatalyst and sustainable material for address contaminant pollution and water splitting. However, the insufficient visible light absorption and fast charge recombination of carbon nitride have limited its practical application. Herein, the self-assembly carbon nitride (denoted as TCN) by molecular doping copolymerization of urea and 2-thiobarbitucid acid (TA) was prepared. XPS and elemental analytical results indicated that TA was doped in the framework of carbon nitride successfully. The self-assembly copolymerization would result in the change of morphology, intrinsic electron and band structure of carbon nitride. Theoretical calculations and experiments confirm that the band gap of TCN could be adjusted by changing the amount of 2-thiobarbitucid acid. Moreover, the efficiency of charge carrier transfer and separation was greatly enhanced. As a result, the optimized photocatalyst TCN-0.03 exhibited superior activity with a high reaction rate of 0.058 min-1 for the degradation of sulfamethazine under visible light irradiation, which is 4.2 times higher than that of urea based carbon nitride (U-CN). As a multifunctional photocatalyst, TCN-0.03 showed enhanced activity for hydrogen production (55 μmol h-1), which was 11 times higher than U-CN. The apparent quantum efficiency reached to 4.8% at 420 nm. A possible mechanism was proposed to explain the photocatalytic reaction process. This work provides insight into the rational design of modified carbon nitride by other organic monomers copolymerization to enhance the photocatalytic activity.
关键词： Photocatalytic degradation,Photocatalytic hydrogen evolution,Carbon nitride,Charge carriers transfer,Molecular doping copolymerization
更新于2025-09-09 09:28:46
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Enhanced Electrocatalysis via Boosted Separation of Hot Charge Carriers of Plasmonic Gold Nanoparticles Deposited on Reduced Graphene Oxide
摘要： The plasmon enhancement on electrocatalysis was investigated on pure Au nanoparticles (AuNPs) and AuNPs-reduced graphene oxide (AuNPs/rGO) hybrid. Upon Localized surface plasmon resonance (LSPR) excitation, hot charge carriers (hot electrons and holes) generate on AuNPs. In the experiments, hot holes are scavenged by glucose, and hot electrons could be efficiently transferred to the external electric circuit under a potential bias, resulting in an observable current enhancement. Then the hot electrons transfer efficiency can be quantitatively compared by the increased current response. It was found that the current density increases more obviously on AuNPs/rGO hybrid compared to pure AuNPs upon light irradiation. Due to the excellent electron mobility of rGO and perfect electron affinity capacity, the hot electrons generated on AuNPs will be efficiently transferred to the closely contacted rGO, then flow into the external circuit generating current. The present study highlights the role of rGO in improving the separation of hot charge carriers to promote the photocatalysis reactions.
关键词： Au nanoparticles (AuNPs),Hot charge carriers,Localized surface plasmon resonance (LSPR),Graphene,Electrochemical method
更新于2025-09-04 15:30:14
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Rational design of yolk–shell nanostructures for photocatalysis
摘要： Photocatalysis is a promising route to convert solar energy into chemical energy directly, providing an alternative solution to environment and natural resource problems. Theoretically, all photocatalytic reactions are driven by charge carriers whose behavior can be divided into charge generation, separation, migration and surface reactions. Efficiencies of charge utilization in every step determine the overall performance of photocatalysis. Yolk–shell (YS) structures can provide an ideal platform for the efficient utilization of charge carriers. Typically, a YS structure is constructed from a hollow shell and an inner core, which can enhance light scattering in the hollow space and provide a large surface to create sufficient active sites, both of which can significantly improve the efficacy of charge utilization. Additionally, many strategies can be adopted to modify the YS structure for further enhancement of charge behaviors in every step. Existing reviews about YS structures mainly concentrate on the universality of the application of YSs, while the strategies to improve photocatalytic performance based on YSs have not been elaborately illustrated. This review describes the classification, synthesis, formation mechanism of YS structures and the rational regulation of the behaviors of photogenerated charge carriers, aiming at their effective utilization based on YS structures in heterogeneous photocatalytic reactions.
关键词： Charge carriers,Heterogeneous photocatalytic reactions,Solar energy conversion,Yolk–shell structures,Photocatalysis
更新于2025-09-04 15:30:14