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Carbon dots (CDs) are ideal fluorophores for optoelectronic devices. However, it is still a great challenge to obtain CDs with high solid‐state photoluminescence quantum yields (PLQYs). In this work, it is first reported that the barium‐doped CDs (Ba‐CDs), which can be simply synthesized on a large scale via a direct one‐step heating approach using an open vessel. The as‐synthesized Ba‐CDs exhibit ultrabright luminescence both in liquid and solid states. The as‐synthesized Ba‐CDs with a scale of 8.6 g per batch show a Stokes shift of ≈0.68 eV and high PLQYs of 80.8% and 66.8% in liquid and solid state, respectively. Interestingly, an efficient fluorescence enhancement phenomenon occurs when Ba‐CDs are mixed with polyvinylpyrrolidone (PVP), which reveals the critical issue of compatibility between CDs and polymer matrix can be well resolved. As a proof‐of‐concept, the Ba‐CDs are employed as fluorophores for high‐efficiency luminescent solar concentrator (LSC) fabrication. The Ba‐CDs@PVP‐based LSC has a PLQY of 88.78%, showing a breakthrough optical conversion efficiency of 7.16% and power conversion efficiency of 6.87% under natural light irradiation (40 mW cm−2). The results demonstrate the potential application of the ultrabright Ba‐CDs in efficient photovoltaic devices. [ABSTRACT FROM AUTHOR]

Colloidal indium phosphide (InP) quantum dots (QDs) have attracted a great attention for their excellent optical properties, and they are a promising candidate for potential applications in optoelectronic devices, such as photocatalysis, light emitting diodes, and bioimaging. However, their use for luminescent solar concentrators (LSCs) has been limited owing to their low optical efficiency, which is because of the energy loss due to the strong overlap between their emission and absorption spectra. Here, we synthesized pyramidal InP/ZnSe QDs based on aminophosphine as the phosphorus precursor by adding hydrofluoric acid to remove the oxides on the InP core surface before the growth of a ZnSe shell. Through researching the exciton dynamic of InP/ZnSe QDs with different shell thicknesses, we found that a thick shell can stabilize the 1Pe energy state of the InP core, thus decreasing the spectral overlap in the overall QDs. As a proof of concept, we demonstrated a highly efficient LSC based on "giant" InP/ZnSe QDs, which exhibited an external optical efficiency of 2.5% and a power conversion efficiency of 2% (5 × 5 × 0.5 cm3) upon simulated sunlight illumination (100 mW/cm2), which is among the best reported LSCs based on InP QDs. Pyramidal "giant" InP/ZnSe QDs hold great potential for the breakthrough development in the field of eco-friendly QD-based LSCs. [ABSTRACT FROM AUTHOR]

Carbon quantum dots (C-dots) showed excellent structure-tunable optical properties, mainly composed of carbon, nitrogen and oxygen. They have been used for various types of solid-state optical devices. Due to the photoluminescence quenching caused by aggregation, it is a challenge to produce high quantum yield and large Stokes shift C-dots via controllable and simple approaches. In this work, we demonstrated a microwave assisted heating approach for the high-quality C-dots production with ten grams scale per batch in less than 4 min. The addition of metal cation promoted the formation of the foam-structure by forming carboxyl-metal-amine complex, enabling the spatial confined growth of the C-dots in a solid-state, contributing to the high quantum yield (QY) of 73% with a Stokes shift of 0.65 eV. By tuning the structure of the C-dots, excitation dependent and independent photoluminescent (PL) behavior were achieved because of the formation of the different types of energy states evidenced by transient PL and femtosecond transient absorption spectroscopy. These optical properties enable the C-dots to be successfully integrated in luminescent solar concentrators (LSCs), having an external optical efficiency of 3.0% and a power conversion efficiency of 1.3% (225 cm2) and an excitation-dependent high-level anticounterfeiting fluorescent code, showing a great potential for solid-state optical system. [Display omitted] • Gram-scale high-quality C-dots through microwave-assisted heating in short time (10 g/batch in 4 min). • High quantum yield (73%) with a Stokes shift of 0.65 eV induced by addition of metal cations. • High optical (3.0%) and PCE (3.0%) large-area (225 cm [2]) luminescent solar concentrators produced. • Excitation-dependent high level anticounterfeiting flourecent code demonstrated. [ABSTRACT FROM AUTHOR]

Luminescent solar concentrators (LSCs) have received significant attention because of their low cost, large-area and high efficiency sunlight energy harvesting. Colloidal core/shell quantum dots (QDs) are promising candidates as absorbers/emitters in LSCs. However, due to the limitation of QDs properties and device architectures, LSCs fabricated using QDs still face the challenges of low optical efficiency and limited long-term stability for the large-area LSCs. In this work, we synthesized CdSe/CdS QDs, and found that higher CdS shell growth temperature results in improved uniformity in structure and morphology and more suitable optical properties. Based on the CdSe/CdS QDs, a large-area (∼100 cm2) sandwich structure luminescent solar concentrator (LSC) was fabricated. By laminating the QDs layer between two sheets of optical clear glass, the reabsorption losses of the device can be reduced due to the decrease of photon escape. The as-fabricated sandwich structure device exhibits an external optical efficiency of ∼ 2.95% under natural sunlight illumination, which represents a 78% enhancement in efficiency over the single layer film LSCs based on CdSe/CdS QDs. More importantly, the sandwich structure can protect the QDs interlayer from the impact of the ambient environment (e.g. oxygen, moisture and alkalinity) and enhance the long-term stability of LSCs. Our work shows that the use of suitably tuned core-shell QDs and the sandwich structure in LSC architecture can dramatically enhance the external optical efficiency of LSC devices based on CdSe/CdS QDs. Photograph of the sandwich structure LSC based on CdSe/CdS QDs. Image 1 • We report a large-area (∼100 cm2) sandwich structure LSC based on CdSe/CdS QDs. • The sandwich structure LSC exhibits an external optical efficiency of ∼2.95%. • The laminated LSC can enhance the stability of devices compared to single layer LSC. [ABSTRACT FROM AUTHOR]

Luminescent solar concentrators (LSCs) can serve as large-area sunlight collectors for photovoltaic (PV) cells, reducing the cost of PV generated power. Typical LSCs consist of optical waveguides doped with highly emissive fluorophores e.g. quantum dots (QDs) or dyes/polymers which are required to exhibit high optical efficiency and long-term stability. Compared to conventional fluorophores, carbon dots (C-dots) have superior advantages of non-toxicity, environmental friendliness, low-cost and simple preparation using abundant carbon based feedstock. Here, we demonstrate large-area LSCs (up to 100 cm 2 ) using colloidal C-dots. Two types of LSCs were fabricated by either incorporating oil-soluble oleylamine-treated C-dots into photo-polymerized poly(lauryl methacrylate) (PLMA) or spin-coating the water-soluble C-dots/polyvinylpyrrolidone (PVP) mixture on the glass substrate. LSCs based on C-dots/PLMA exhibit a quantum efficiency of 4% (geometric (G) factor of 38) and an optical efficiency of 1.1% (100 cm 2 , G factor of 12.5) of tandem thin-film LSCs based on C-dots/PVP was achieved under one sun illumination. This performance is comparable to those of LSCs based on inorganic QDs with similar G factor. The LSCs based on C-dots are highly air-stable without any noticeable variation in photoluminescence under ultraviolet illumination (1.3 W/cm 2 ) for over 12 h. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

As a large-area solar radiation collector, luminescent solar concentrators (LSCs) can be used as power generation units in semitransparent solar windows, modernized agricultural greenhouses and building facades. However, the external optical efficiency and long-term stability of the LSCs limit their practical applications due to the sensitivity of the emitters to the light and environmental conditions. Here, we used the concept of "laminated glass" to prepare LSCs, which consist of two waveguide layers and the quantum dots (QDs)/polymer interlayer, and we tune the refractive index of the different parts of the system to improve the external optical efficiency and stability of the LSCs, simultaneously. The waveguide layer can be glass, quartz, polymethyl methacrylate (PMMA) and other transparent materials. The CdSe/CdS core/shell QDs were used as fluorophores to prepare the interlayer of the LSCs. The external optical efficiency of the laminated LSCs is associated with the refractive index of the three layers: the closer the refractive index, the higher the η opt. The highest external optical efficiency of 3.4% has been achieved for the laminated PMMA/QDs-polymer/PMMA LSCs, which improved ~92% compared to the single-layered CdSe/CdS based LSCs. To the best of our knowledge, this is the highest efficiency for the LSCs based on CdSe/CdS QDs. These results pave the way to realize high efficiency laminated windows as power generation units by suitably tuning the structure of the LSC, and provide the theoretical guidance for the LSCs utilized in building integrated photovoltaics. External optical efficiency of the laminated LSCs with different refractive index configuration. Inset is the photograph of the laminated LSCs based on CdSe/CdS QDs. Image 1 • We report refractive index-engineered laminated LSCs based on CdSe/CdS QDs. • The optical efficiency strongly depends on the refractive index configuration. • The laminated LSCs exhibits an optimal external optical efficiency of ~3.44%. [ABSTRACT FROM AUTHOR]

Luminescent solar concentrators (LSCs) are able to efficiently harvest solar energy through large‐area photovoltaic windows, where fluorophores are delicately embedded. Among various types of fluorophores, all‐inorganic perovskite nanocrystals (NCs) are emerging candidates as absorbers/emitters in LSCs due to their size/composition/dimensionality tunable optical properties and high photoluminescence quantum yield (PL QY). However, due to the large overlap between absorption and emission spectra, it is still challenging to fabricate high‐efficiency LSCs. Intriguingly, zero‐dimensional (0D) perovskites provide a number of features that meet the requirements for a potential LSC absorber, including i) small absorption/emission spectral overlap (Stokes shift up to 1.5 eV); ii) high PL QY (>95% for bulk crystal); iii) robust stability as a result of its large exciton binding energy; and iv) ease of synthesis. In this work, as a proof‐of‐concept experiment, Cs4PbBr6 perovskite NCs are used to fabricate semi‐transparent large‐area LSCs. Cs4PbBr6 perovskite film exhibits green emission with a high PL QY of ≈58% and a small absorption/emission spectral overlap. The optimized LSCs exhibit an external optical efficiency of as high as 2.4% and a power conversion efficiency of 1.8% (100 cm2). These results indicate that 0D perovskite NCs are excellent candidates for high‐efficiency LSCs compared to 3D perovskite NCs. [ABSTRACT FROM AUTHOR]

The fabrication of a low reabsorption emission loss, highly efficient luminescent solar concentrator (LSC), based on near infrared core/shell quantum dots embedded in a polymer matrix is demonstrated in article number 1501913, by Haiguang Zhao, Alberto Vomiero, Federico Rosei, and co‐workers. The semi‐transparent LSC exhibits an optical efficiency of 6.1% for a geometric factor G equal to 10, which is unprecedented for planar LSCs based on near infrared quantum dots. [ABSTRACT FROM AUTHOR]

• A triple-layer LSC was fabricated, with an external optical efficiency of 9.1 %, and a PCE of 6.0 %. • The blue-, green- and orange- emitting C-dots have a quantum yield of 90 %, 73 %, and 72 %. • The multilayer LSCs have high CRI above 80 and AVT above 70 %, suitable for efficient BIPVs. Compared to the silicon-based photovoltaics, large-area luminescent solar concentrators (LSCs) can be used as smart PV window for building-integrated photovoltaics (BIPVs). However, because of the low quantum yield of the fluorophores, and reabsorption energy loss, the current obtained large-area LSCs have low optical efficiency. Herein, we demonstrated highly efficient and semitransparent multilayer LSCs based on three types of carbon quantum dots (C-dots). The blue and green C-dots were synthesized using vacuum heating approach and the orange C-dots were synthesized using solvothermal approach. The as-prepared B-, G- and O-C-dots have the QYs of 90 %, 73 % and 72 %, respectively, with large Stokes shift (0.37–0.73 eV). By optimizing the concentration of the C-dots in each layer, the best LSC (100 cm2) with multilayer structure exhibited an external optical efficiency of 9.1 %, and a power conversion efficiency (PCE) of 6.0 %, which are higher than that of most of reported LSCs. The simulations indicate that optimized multilayer LSCs could have a theoretical external optical efficiency over 12 % for 1 m2 devices. Besides high optical efficiency, the multilayer LSCs also have high Color Rendering Index (above 80) and high average visible transmission (above 70 %), which make the as-prepared LSCs suitable for potential commercial BIPVs. [ABSTRACT FROM AUTHOR]

• Eco-friendly CuGaAlS/ZnS core/shell QDs were successfully synthesized. • Optical properties of QDs can be tuned by varying the copper contents. • The optimized QDs show a high PLQY of 91% with a large Stokes-shift. • High-performance and large-area QDs-based LSC device is fabricated. Luminescent solar concentrators (LSCs) fabricated using colloidal quantum dots (QDs) are considered as promising cost-effective solar collectors for future building-integrated photovoltaics (BIPV). Nevertheless, the solar-to-electricity conversion efficiency of the LSCs is commonly low due to limited quantum efficiency and large reabsorption loss of QDs. In addition, most of the efficient LSCs contain heavy metal-based QDs, limiting their potential commercial applications. Herein, we demonstrate a novel type of eco-friendly CuGaAlS/ZnS (CGAS/ZnS) core/shell QDs with efficient surface passivation and manipulated their optical properties by varying the copper contents, which effectively regulates the intrinsic band structure and radiative recombination dynamics. As a result, the optimal Cu-deficient CGAS/ZnS core/shell QDs exhibit the highest photoluminescence quantum yield (PLQY) of ∼ 91 % and large Stokes shift (∼0.81 eV). The prepared QDs were applied as emitters and integrated in polymer matrix to fabricate LSCs (10 × 10 × 0.15 cm3), delivering an unprecedented power conversion efficiency (PCE) of 4.29 % under standard one sun AM 1.5G illumination (100 mW cm−2). Our results imply that tuning the components of multinary environment-friendly core/shell QDs endows the feasibility to realize low-cost and high-efficiency BIPV applications. [ABSTRACT FROM AUTHOR]