Large-area Luminescent Solar Concentrators Research Articles

Highly efficient and stable tandem luminescent solar concentrators based on carbon dots and CuInSe2-xSx/ZnS quantum dots.

Semi-transparent large-area luminescent solar concentrators (LSCs) have been considered an essential part of zero-energy or low-energy consuming buildings in the future. Inorganic colloidal quantum dots (QDs) are promising candidates for LSCs due to the advantages of a tunable bandgap, engineered large Stokes shift, and relatively high photoluminescence (PL) quantum yield. However, LSCs that are fabricated using colloidal quantum dots exhibited an inferior stability under long-term illumination, demanding great efforts to explore the highly stable LSCs. Herein, we fabricated large-area (∼100 cm2) tandem LSCs based on highly stable carbon dots (CDs) and highly luminescent near-infrared emitting CuInSe2-xSx/ZnS (CuInSeS/ZnS) QDs. Coupled with a Si diode as a reference, the power conversion efficiency of the corresponding tandem (dimensions: 10 × 10 × 0.5 cm3) and single LSCs (dimensions: 10 × 10 × 0.3 cm3) based on CuInSeS/ZnS QDs under one sun illumination are 0.46% and 0.5%, respectively. For single CuInSeS/ZnS QD based LSCs at a low concentration (0.039 wt%), external and internal quantum efficiencies reach up to 2.87% and 36.37%, respectively. After UV illumination for 8 h, bottom LSCs based on CuInSeS/ZnS QDs retain 93.22% of the initial PL emission, which is higher than that of LSCs (∼80%) without the CD protection. The highly efficient and stable tandem LSCs employing green CDs and NIR CuInSeS/ZnS QDs as PL emitters pave the way for the realization of large area building-integrated photovoltaic (BIPV) devices.

Highly efficient and high color rendering index multilayer luminescent solar concentrators based on colloidal carbon quantum dots

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.

Luminescent solar concentrator efficiency versus edge solar cell coverage.

This Letter introduces an analytical approach to estimate the waveguiding efficiency of large-area luminescent solar concentrators (LSCs), where the edges are covered by a varied number of mirrors and solar cells. The model provides physically relevant description in the whole range of optical (absorption, scattering) and geometrical (size) parameters of rectangular LSCs. A 19 × 19cm2 silicon quantum dot-based LSC has been fabricated to verify the theory. Within an experimental error, the predicted waveguiding efficiency matched well the measured one. A critical LSC size, beyond which a part of the device turns inactive, has been determined as N/α for N attached solar cells (one or two) and LSC material absorption coefficient α. This model provides a straightforward waveguiding analysis tool for large-area LSCs with different structural parameters relevant for both high concentration ratio and glazing applications.

Spatially Resolved Optical Efficiency Measurements of Luminescent Solar Concentrators.

Luminescent solar concentrators (LSCs) are able to concentrate both direct and diffuse solar radiation, and this ability has led to great interest in using them to improve solar energy capture when coupled to traditional photovoltaics (PV). In principle, a large-area LSC could concentrate light onto a much smaller area of PV, thus reducing costs or enabling new architectures. However, LSCs suffer from various optical losses which are hard to quantify using simple measurements of power conversion efficiency. Here, we show that spatially resolved photoluminescence quantum efficiency measurements on large-area LSCs can be used to resolve various loss processes such as out-coupling, self-absorption via emitters, and self-absorption from the LSC matrix. Further, these measurements allow for the extrapolation of device performance to arbitrarily large LSCs. Our results provide insight into the optimization of optical properties and guide the design of future LSCs for improved solar energy capture.

Boosting efficiency of luminescent solar concentrators using ultra-bright carbon dots with large Stokes shift.

Luminescent solar concentrators (LSCs) are able to collect sunlight from a large-area to generate electric power with a low cost, showing great potential in building-integrated photovoltaics. However, the low efficiency of large-area LSCs caused by the reabsorption losses is a critical issue that hampers their practical applications. In this work, we synthesized novel yellow emissive carbon dots (CDs) with a large Stokes shift of 193 nm, which exhibit nearly zero reabsorption. The quantum yield (QY) of the yellow emitting CDs is up to 61%. The yellow emitting CDs can be employed to fabricate high-performance large-area LSCs due to successful suppression of the reabsorption losses. The as-prepared LSCs are able to absorb 14% of the sunlight as the absorption of the CDs matches well with the sun's spectrum. The large-area LSC (10 × 10 cm2) with a laminated structure based on the yellow emitting CDs achieves an optical conversion efficiency (ηopt) of 4.56% and power conversion efficiency (ηPCE) of 4.1% under natural sunlight (45 mW cm-2), which are significantly higher than other previously reported works with similar sizes. Furthermore, the prepared high-performance LSCs show good stability. This method of synthesizing novel CDs for high-efficiency LSCs provides a useful platform for future study and practical application of LSCs.

Assessment of large-area luminescent solar concentrators as building-integrated geodesic dome panels

Assessment of large-area luminescent solar concentrators as building-integrated geodesic dome panels

Engineering high-emissive silicon-doped carbon nanodots towards efficient large-area luminescent solar concentrators

Luminescent solar concentrators (LSCs) are devices that can collect sunlight from a large area, concentrating it at the borders of the slab, to achieve efficient photovoltaic conversion when small area solar cells are placed at their edges, realizing building-integrated photovoltaics. Efficient luminophores in terms of high luminescence quantum yield are needed to obtain high-performance LSCs. A key point is the ability to engineer the Stokes shift (i.e. the difference between the maximum of the absorption and emission spectra), to minimize reabsorption processes. In this work, we report novel silicon-doped carbon nanodots (Si-CDs) with an ultrahigh quantum yield (QY) up to 92.3% by a simple hydrothermal method. Thin-film structured LSCs (5 × 5 × 0.2 cm3) with different concentrations of Si-CDs are prepared by dispersing the Si-CDs into polyvinyl pyrrolidone (PVP) matrix, and the optimal power conversion efficiency (PCE) of LSCs can be as high as 4.36%, which is nearly 2.5 times higher than that prepared with silicon-undoped CDs. This Si-CDs/PVP film LSC has a high QY of 80.5%. A large-area LSC (15 × 15 cm2) is also successfully fabricated, which possesses a PCE of 2.06% under natural sunlight irradiation (35 mW·cm−2), one of the best reported values for similar size LSCs. The efficient Si-CDs as luminescent substances for high-efficiency large-area LSCs will further give an impetus to the practical exploitation of LSCs.

Luminescent solar concentrator based on large-Stokes shift tetraphenylpyrazine fluorophore combining aggregation-induced emission and intramolecular charge transfer features

This study presents bulk configuration large-area luminescent solar concentrators (LSCs) incorporating a novel organic fluorophore (TPP1) based on tetraphenylpyrazine core symmetrically functionalized with electron-rich dimethylamine (donor) and electron-deficient cyano (acceptor) moieties. As confirmed experimentally and validated through a computational approach, TPP1 exhibits aggregation-induced emission and a large Stokes shift due to intramolecular charge transfer, making it an excellent candidate as a fluorophore in poly(methyl methacrylate) based LSCs. Based on promising photophysical properties, TPP1 LSCs with suitable concentration showed an internal and external photon efficiency of 23.7% and 2.33% under AM 1.5G illumination, respectively. The size scalability (up to 100 cm length) of TPP1 LSCs was also evaluated by employing analytical models. Moreover, the power conversion efficiency of 10 × 10 × 0.3 cm3 LSC (geometrical factor 8.33) was found to be 0.66% and 0.34%, with and without scattering background, respectively. Such outstanding optical and PV performances of TPP1 LSCs clearly illustrate that TPP1 with combined AIE and ICT features is a viable alternative to most organic dyes. Additionally, stability and aesthetics analysis of TPP1 LSCs also suggest their long-term use and compatibility with the built environment.

Large‐Area Semi‐Transparent Luminescent Solar Concentrators Based on Large Stokes Shift Aggregation‐Induced Fluorinated Emitters Obtained Through a Sustainable Synthetic Approach

AbstractIn this study, the design, fabrication, and characterization of semi‐transparent large‐area luminescent solar concentrators (LSCs) in thin‐film configuration is reported, incorporating a novel organic luminophore (PFPBNT) emitter based on a π‐conjugated core flanked by two naphthothiophene units obtained through a chemically sustainable synthetic approach. As found experimentally and validated through computational modeling, PFPBNT exhibits aggregation‐induced emission (AIE) behavior, broad absorption in the UV–vis spectrum and significant Stokes shift (≈4632 cm–1), thereby making it an excellent candidate as luminophore in thin‐film LSCs based on a poly(methyl methacrylate) (PMMA) matrix, where it is found to show good compatibility, homogeneous distribution, and excellent photostability. After extensive device optimization, PFPBNT/PMMA LSCs with suitable luminophore concentration (12.5 wt%) showed an internal photon efficiency of 17.3% at a geometrical gain of 6.25 under solar‐simulated illumination. The size scalability of these systems was also evaluated by means of ray‐tracing simulations on devices of up to 1 m2 surface area. This work demonstrates semi‐transparent large‐area thin‐film LSCs incorporating chemically sustainable AIEgen luminophores, thus opening the way to the development of synthetically affordable, efficient, and stable emitters for the photovoltaic field.

Gram-scale synthesis of carbon quantum dots with a large Stokes shift for the fabrication of eco-friendly and high-efficiency luminescent solar concentrators

Highly efficient large-area luminescent solar concentrators (LSCs) were demonstrated using colloidal C-dots. The large-area LSC (225 cm2) exhibited an external optical efficiency of 2.2% (under natural sun irradiation, 60 mW cm−2).

Large-area luminescent solar concentrator utilizing donor-acceptor luminophore with nearly zero reabsorption: Indoor/outdoor performance evaluation

Luminescent solar concentrators (LSCs) are light-guides doped with luminophores that can spectrally and spatially concentrate solar radiation. With the ability to harvest both direct and diffuse light, LSCs are considered attractive prospects for building-integrated photovoltaic applications. However, it is still challenging to develop organic luminophores based large-area LSCs that work well in various illumination conditions. Reabsorption, caused by small stokes shift of typical organic luminophores, often limits the performance of large-area LSCs. This study reports an indoor and outdoor performance of large-area (≥100 cm2) LSCs that employ a donor-acceptor luminophore with a large Stokes shift. The largest (400 cm2) LSC demonstrates an optical efficiency (ηopt) of 5.5% and 7.6% under outdoor (AM 1.5G) and indoor (white LED) illuminations, respectively. Furthermore, the aesthetic and visual comfort parameters such as chromaticity coordinates, color rendering index, and average visible transmission are obtained that suggest the suitability of our LSCs for a built environment.

Spectral response of large-area luminescent solar concentrators.

Measuring the spectral response (SR) of large-area (>100cm2) luminescent solar concentrators (LSCs) has proven difficult because common laboratory photovoltaic (PV) instruments that offer monochromatic incidence measure devices with limited sizes (typically <50cm2). This report addresses this issue through a method called regional measurements. In this method, large-area LSCs are configured to small surface and edge regions, which are sequentially illuminated and measured, respectively. The measured SRs of large-area LSCs are consistent with those from the conventional method and the Monte Carlo ray-tracing simulation. This method is also applied to analyze scattering effects in the LSCs, showing the relationships of the scattering-induced power gain and power loss to the surface root-mean-squared roughness (Rq) of the devices. The results explain why the PV performance of the LSCs can be improved through proper surface scattering treatment.

Regional measurements to analyze large-area luminescent solar concentrators

Abstract Experimentally analyzing the photovoltaic (PV) performance and the photon transport mechanism of large-area luminescent solar concentrators (LSCs) (>200 cm2) has proven difficult because common solar simulators and integrating spheres have limited measuring capacity. This report introduces an approach of regional measurements to address these issues using common laboratory instruments. In this approach, the LSC is configured to have different surface and edge regions. The surface regions are sequentially illuminated by a low-cost solar simulator, and the edge regions sequentially measured by a small-area solar cell or a general photoluminescence (PL) spectrometer. The methodology is validated through the comparison with the conventional method and Monte Carlo ray-tracing simulation in the study of the PV performance of a series of R305-based LSCs. Experimental results from the regional measurements reveal important the photon transport mechanism of the LSCs. The results show that severe photon transport loss exists within a surface distance (dsurf) of 5 inches (12.7 cm), and photons with the longest average transport distance ( max) experience number of absorption events (Nabs) for an average of 11.3 times. The approach of regional measurements can effectively measure the PV performance and investigate the photon transport mechanism of large-area LSCs.

High-Performance Large-Area Luminescence Solar Concentrator Incorporating a Donor–Emitter Fluorophore System

A high-performance large-area luminescent solar concentrator (LSC) is demonstrated, fabricated via careful choice of the fluorophore system, waveguide material, and coupled photovoltaic (PV) cells. Doctor-blading was used to deposit a PMMA–dye blend film on the surface of a PMMA planar waveguide to fabricate the large-area LSC with dimensions of 20 × 20 × 0.1 cm3. A perylene diimide-based donor–emitter fluorophore pair was chosen to both improve the photoluminescent quantum yield and reduce the luminescence reabsorption. Three types of photovoltaic cells were coupled to the LSC to optimize the device output performance. With the combination of the donor–emitter fluorophore pair chosen, the PMMA-based LSC deposition process and coupled perovskite PV cells, the LSC has an experimental flux gain of 7.4 at a geometric gain of 50 (G = 50) under 1 sun irradiation, with a power conversion efficiency of 2.6%.

Fabrication of highly emissive and highly stable perovskite nanocrystal-polymer slabs for luminescent solar concentrators

The high-performance light-management slabs made of low-cost, highly emissive, and ultra-stable nanocrystal (NC)-polymer composites are desirable for application in large-area luminescent solar concentrators (LSCs).

Silicon Quantum Dot–Poly(methyl methacrylate) Nanocomposites with Reduced Light Scattering for Luminescent Solar Concentrators

Silicon quantum dots with indirect bandgap photoluminescence are promising luminophores for large-area luminescent solar concentrators (LSCs). However, if commercially viable devices are to be achi...

The solar noise barrier project: 2. The effect of street art on performance of a large scale luminescent solar concentrator prototype

Noise barriers have been used worldwide to reduce the impact of sound generated from traffic on nearby areas. A common feature to appear on these noise barriers are all manner of graffiti and street art. In this work we describe the relative performance of a large area luminescent solar concentrator (LSC) noise barrier before and after application of street art to one surface. Comparisons are made of performance of East/West facing panels during a sunny day. It is shown that the edge mounted solar cells that are further away from the artwork perform at about 80% of their original performance level, while cells mounted nearby show greater performance decreases, suggesting that the effect of street art is primarily a localized effect. Furthermore, we demonstrate that illumination by sunlight from the rear side of the panel, opposite to the artwork shows less of a performance drop. In summary, the overall performance of a large-scale prototype LSC device is affected by the application of street art due to blocking solar access to the surface, but the effect is mostly confined to areas in the immediate vicinity of the surface modification, and the remaining panel area continues to function at a reasonable level.

Doctor-blade deposition of quantum dots onto standard window glass for low-loss large-area luminescent solar concentrators

Luminescent solar concentrators can be used to harvest sunlight over large areas at low cost, and are promising for building-integrated photovoltaics. Li et al. fabricate such devices from silica-coated colloidal quantum dots having internal quantum efficiencies over 10% on tens of centimetres.

Spectroscopic and Device Aspects of Nanocrystal Quantum Dots.

The field of nanocrystal quantum dots (QDs) is already more than 30 years old, and yet continuing interest in these structures is driven by both the fascinating physics emerging from strong quantum confinement of electronic excitations, as well as a large number of prospective applications that could benefit from the tunable properties and amenability toward solution-based processing of these materials. The focus of this review is on recent advances in nanocrystal research related to applications of QD materials in lasing, light-emitting diodes (LEDs), and solar energy conversion. A specific underlying theme is innovative concepts for tuning the properties of QDs beyond what is possible via traditional size manipulation, particularly through heterostructuring. Examples of such advanced control of nanocrystal functionalities include the following: interface engineering for suppressing Auger recombination in the context of QD LEDs and lasers; Stokes-shift engineering for applications in large-area luminescent solar concentrators; and control of intraband relaxation for enhanced carrier multiplication in advanced QD photovoltaics. We examine the considerable recent progress on these multiple fronts of nanocrystal research, which has resulted in the first commercialized QD technologies. These successes explain the continuing appeal of this field to a broad community of scientists and engineers, which in turn ensures even more exciting results to come from future exploration of this fascinating class of materials.

Enhanced Photon Collection in Luminescent Solar Concentrators with Distributed Bragg Reflectors

Escape cone loss is one of the primary limiting factors for efficient photon collection in large-area luminescent solar concentrators (LSCs). The Stokes shift of the luminophore, however, opens up an opportunity to recycle the escaped luminescence at the LSC front surface by utilizing a photonic band-stop filter that reflects photons in the luminophore’s emission range while transmitting those in its absorption range. In this study, we examine the functional attributes of such photonic filter designs, ones realized here in the form of a distributed Bragg reflector (DBR) fabricated by spin-coating alternating layers of SiO2 and SnO2 nanoparticle suspensions onto a supportive glass substrate. The central wavelength and the width of the photonic stopband were programmatically tuned by changing the layer thickness and the refractive index contrast between the two dielectric materials. We explore the design sensitivities for a DBR with an optimized stopband frequency that can effectively act as a top angle-res...