Luminescent solar concentrators (LSCs) can serve as large-area sunlight collectors, are suitable for applications in high-efficiency and cost-effective photovoltaics (PVs), and provide adaptability ...to the needs of architects for building-integrated PVs, which makes them an attractive option for transforming buildings into transparent or non-transparent electricity generators. Compared with traditional organic dyes, colloidal semiconducting quantum dots (QDs) are excellent candidates as emitters for LSCs because they exhibit wide size/shape/composition-tunable absorption spectra ranging from ultraviolet to near infrared, significantly overlapping with the solar spectrum. They also feature narrow emission spectra, high photoluminescence quantum yields, high absorption coefficients, solution processability and good photostability. Most importantly, QDs can be engineered to provide a minimal overlap between absorption and emission spectra, which is key to the realization of large-area LSCs with largely suppressed reabsorption energy losses. In this review article, we will first present and discuss the working principle of LSCs, the synthesis of colloidal QDs using wet-chemistry approaches, the optical properties of QDs, their band alignment and the intrinsic relationship between the band energy structure and optical properties of QDs. We focus on emerging architectures, such as core/shell QDs. We then highlight recent progress in QD-based LSCs and their anticipated applications. We conclude this review article with the major challenges and perspectives of LSCs in future commercial technologies.
This review summarizes the recent progress, challenges and perspectives of luminescent solar concentrators based on colloidal quantum dots
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harnessing their properties.
Astounding development of organic-inorganic halide perovskite solar cells (PSCs) in the past decade has been led by three-dimensional (3D) perovskites. Nevertheless, the concern over the stability of ...3D PSCs casts a shadow on their real-world applications. By adopting various technological and scientific approaches, some progress has been made in improving the stability of 3D perovskite devices. Nonetheless, the best, definitive solution consists in improving the inherent chemical stability of the halide perovskite itself. Two-dimensional (2D) perovskites, on the other hand, display excellent stability under ambient conditions and have been recognized as an alternative to their 3D analogs. Although the first generation 2D PSCs have shown relatively lower photovoltaic performance, recent reports suggest that they are also capable of achieving high power conversion efficiency well beyond 20%. In the wake of the recent resurgence of 2D halide perovskite materials, we review their structural and optoelectronic properties, followed by an extensive analysis of recent progress in 2D PSCs.
Two-dimensional perovskites are an attractive alternative to 3D perovskites for solar cell application as they directly address a critical issue of stability of 3D perovskite solar cells, while achieving similarly high power conversion efficiencies.
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Nowadays, metal nanoparticles (NPs) have been considered as highly promising functional materials, impacting virtually all the fields of science and technologies. Numerous ...wet-chemical approaches have been developed to synthesize metal NPs with various components and structures. Although successful, impurities, such as additives and reaction residuals, usually remain in products. Recently, an alternative method, pulsed laser ablation in liquid (PLAL) phase has attracted increasing attention for colloidal NP preparation, since it can realize a chemical-free environment, leading to the formation of a “clean” NP dispersion. This unique feature makes the PLAL method and resulting metal NPs extremely attractive for catalytic applications, since catalytic reaction efficiency is strongly dependent on the surface feature of metal NPs. Usually, a surfactant-free, “bare” metal surface is highly desired for catalysis as it favors the access of the reactants to the surface active sites of metal NPs. Due to the absence of ligand or stabilizer molecules on the surface of PLAL-NPs, it is expected that these PLAL-NPs can exhibit higher catalytic activity in comparison to their chemically synthesized counterparts. In this review, we briefly introduce some recent advances on the synthesis of PLAL-metal NPs and some of their important catalytic applications.
Thanks to the helpful discussions and strong support provided by the Publisher and Editorial Staff of Nanomaterials, I was appointed as a section Editor-in-Chief of the newly launched section “Solar ...Energy and Solar Cells” earlier this year (2021) ...
A plasmon and upconversion enhanced broadband photocatalyst based on Au nanoparticle (NP) and NaYF4:Yb3+, Er3+, Tm3+ (NYF) microsphere loaded graphitic C3N4 (g-C3N4) nanosheets (Au-NYF/g-C3N4) was ...subtly designed and synthesized. The simple one-step synthesis of NYF in the presence of g-C3N4, which has not been reported in the literature either, leads to both high NYF yield and high coupling efficiency between NYF and g-C3N4. The Au-NYF/g-C3N4 structure exhibits high stability, wide photoresponse from the ultraviolet (UV), to visible and near-infrared regions, and prominently enhanced photocatalytic activities compared with the plain g-C3N4 sample in the degradation of methyl orange (MO). In particular, with the optimization of Au loading, the rate constant normalized with the catalysts mass of the best-performing catalyst 1 wt % Au-NYF/g-C3N4 (0.032 h–1 mg–1) far surpasses that of NYF/g-C3N4 and g-C3N4 (0.009 h–1 mg–1) by 3.6 times under λ > 420 nm light irradiation. The high performance of the Au-NYF/g-C3N4 nanocomposite under different light irradiations was ascribed to the distinctively promoted charge separation and suppressed recombination, and the efficient transfer of charge carriers and energy among these components. The promoted charge separation and transfer were further confirmed by photoelectrochemical measurements. The 1 wt % Au-NYF/g-C3N4 exhibits enhanced photocurrent density (∼6.36 μA cm–2) by a factor of ∼5.5 with respect to that of NYF/g-C3N4 sample (∼1.15 μA cm–2). Different mechanisms of the photodegradation under separate UV, visible, and NIR illuminations are unveiled and discussed in detail. Under simulated solar light illumination, the involved reactive species were identified by performing trapping experiments. This work highlights the great potential of developing highly efficient g-C3N4-based broadband photocatalysts for full solar spectrum utilization by integrating plasmonic nanostructures and upconverting materials.
Efficiently harvesting solar energy for photocatalysis remains very challenging. Rational design of architectures by combining nanocomponents of radically different properties, for example, ...plasmonic, upconversion, and photocatalytic properties, offers a promising route to improve solar energy utilization. Herein, the synthesis of novel, plasmonic Au nanoparticle decorated NaYF4:Yb3+, Er3+, Tm3+‐core@porous‐TiO2‐shell microspheres is reported. They exhibit high surface area, good stability, broadband absorption from ultraviolet to near infrared, and excellent photocatalytic activity, significantly better than the benchmark P25 TiO2. The enhanced activity is attributed to synergistic effects from nanocomponents arranged into the nanostructured architecture in such a way that favors the efficient charge/energy transfer among nanocomponents and largely reduced charge recombination. Optical and energy‐transfer properties are modeled theoretically to support our interpretations of catalytic mechanisms. In addition to yielding novel materials and interesting properties, the current work provides physical insights that can contribute to the future development of plasmon‐enhanced broadband catalysts.
Au nanoparticle decorated NaYF4:Yb3+, Er3+, Tm3+@TiO2 core@porous‐shell microspheres are successfully prepared and exhibit excellent, stable, and broadband photocatalytic activity from UV up to near‐infrared by rationally applying plasmon and upconversion concepts into photocatalysis.
To enhance the catalytic activity of gold nanoparticles (AuNPs) for the hydrogenation of nitro-aromatic chemicals, Pt was introduced into AuNPs to form "bare" PtAu alloy NPs using a physical ...approach, pulsed laser ablation in liquid (PLAL), on single metal-mixture targets. These PLAL-NPs are deemed to favor catalysis due to the absence of any surfactant molecules on their unique "bare and clean" surface. The PLAL-NPs were facilely assembled onto CeO
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nanotubes (NTs) by simply mixing them without conducting any surface functionalization, representing another advantage of these NPs. Their catalytic activity was assessed in 4-nitrophenol (4-NP) hydrogenation. The reaction catalyzed by alloy-NP/CeO
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-NT catalysts demonstrates a remarkably higher reaction rate in comparison with that catalyzed by pure Au and Pt NPs, and other similar Au and Pt containing catalysts reported recently. A "volcano-like" catalytic activity dependence of the alloy NPs on their chemical composition suggests a strong synergistic effect between Au and Pt in the 4-NP reduction, far beyond the simple sum of their individual contributions. It leads to the significantly enhanced catalytic activity of Pt
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Au
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and Pt
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Au
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alloy NPs, outperforming not only each single constituent, but also their physical mixtures and most recently reported AuNP based nanocatalysts. The favorable d-band center shift of Pt after alloying, and co-operative actions between Pt clusters and nearby Au (or mixed PtAu) sites were proposed as possible mechanisms to explain such a strong synergistic effect on catalysis.
PtAu alloy nanoparticles with unique surface chemistry prepared using the laser ablation method demonstrate interesting synergistic catalytic performance in 4-nitrophenol reduction.
Abstract
Conversion of clean solar energy to chemical fuels is one of the promising and up-and-coming applications of metal–organic frameworks. However, fast recombination of photogenerated charge ...carriers in these frameworks remains the most significant limitation for their photocatalytic application. Although the construction of homojunctions is a promising solution, it remains very challenging to synthesize them. Herein, we report a well-defined hierarchical homojunction based on metal–organic frameworks via a facile one-pot synthesis route directed by hollow transition metal nanoparticles. The homojunction is enabled by two concentric stacked nanoplates with slightly different crystal phases. The enhanced charge separation in the homojunction was visualized by in-situ surface photovoltage microscopy. Moreover, the as-prepared nanostacks displayed a visible-light-driven carbon dioxide reduction with very high carbon monooxide selectivity, and excellent stability. Our work provides a powerful platform to synthesize capable metal–organic framework complexes and sheds light on the hierarchical structure-function relationships of metal–organic frameworks.
This study aims to develop a deep learning model to improve the accuracy of identifying tiny targets on high resolution remote sensing (HRS) images. We propose a novel multi-level weighted depth ...perception network, which we refer to as MwdpNet, to better capture feature information of tiny targets in HRS images. In our method, we introduce a new group residual structure, S-Darknet53, as the backbone network of our proposed MwdpNet, and propose a multi-level feature weighted fusion strategy that fully utilizes shallow feature information to improve detection performance, particularly for tiny targets. To fully describe the high-level semantic information of the image, achieving better classification performance, we design a depth perception module (DPModule). Following this step, the channel attention guidance module (CAGM) is proposed to obtain attention feature maps for each scale, enhancing the recall rate of tiny targets and generating candidate regions more efficiently. Finally, we create four datasets of tiny targets and conduct comparative experiments on them. The results demonstrate that the mean Average Precision (mAP) of our proposed MwdpNet on the four datasets achieve 87.0%, 89.2%, 78.3%, and 76.0%, respectively, outperforming nine mainstream object detection algorithms. Our proposed approach provides an effective means and strategy for detecting tiny targets on HRS images.
The fabrication of a low reabsorption emission loss, high efficient luminescent solar concentrator (LSC) is demonstrated by embedding near infrared (NIR) core/shell quantum dots (QDs) in a polymer ...matrix. An engineered Stokes shift in NIR core/shell PbS/CdS QDs is achieved via a cation exchange approach by varying the core size and shell thickness through the refined reaction parameters such as reaction time, temperature, precursor molar ratio, etc. The as‐synthesized core/shell QDs with high quantum yield (QY) and excellent chemical/photostability exhibit a large Stokes shift with respect to the bare PbS QDs due to the strong core‐to‐shell electrons leakage. The large‐area planar LSC based on core/shell QDs exhibits the highest value (6.1% with a geometric factor of 10) for optical efficiency compared to the bare NIR QD‐based LSCs and other reported NIR QD‐based LSCs. The suppression of emission loss and the broad absorption of PbS/CdS QDs offer a promising pathway to integrate LSCs and photovoltaic devices with good spectral matching, indicating that the proposed core/shell QDs are strong candidates for fabricating high efficiency semi‐transparent large‐area LSCs.
A large‐area semi‐transparent luminescent solar concentrator (LSC) is developed using engineered Stokes shifts in near infrared (NIR) core/shell PbS/CdS quantum dots (QDs). The as‐prepared QD‐based LSC yields a remarkable optical efficiency of 6.1% with geometric factor of 10, which is a record optical efficiency for planar NIR QD‐based LSCs.
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