Film Luminescent Solar Concentrators Research Articles

Constructing highly efficient and ultra-stable (against Temperature, Humidity and Sunlight) luminescent solar concentrators by using dendritic CsPbBr3@SiO2 particles

Conventional perovskite quantum dots (PQDs) suffer long-term stability, further limiting practical application of luminescent solar concentrators (LSCs). In this work, novel dendritic CsPbBr3@SiO2 particles with bright solid-state green light emission and 46 % of photoluminescence quantum yield (PLQY) have first been synthesized via one-step solid-phase calcination method. The dendritic CsPbBr3@SiO2 particles have then been used as fluorescent material for construction of LSCs along with using organosilicon polymers with better compatibility as waveguide materials. Single-layer thin film LSCs and overall curing LSCs are easily prepared by the casting and curing method, exhibiting high external optical efficiency (ηopt) of 7.88 % and 10.92 %, respectively. The maximum internal quantum efficiency (ηint) of thin film LSCs and overall curing LSCs reach 45.09 % and 44.07 %, respectively, while their maximum external quantum efficiency (ηext) of 29.42 % and 34.07 % are obtained, respectively. Importantly, both types of LSCs show excellent stability, maintaining above 92 % of the initial ηopt under high-relative-humidity (RH = 90 %), high-temperature (60 °C) and sunlight exposure conditions for two weeks or room temperature environment for twenty weeks. Moreover, both types of LSCs at optimal conditions have good transparency (>40 % over 515 nm of light wavelength). Otherwise, both types of LSCs have higher ηopt than that of the previous related work.

Study of the Scattering Effect by SiO2 Nanoparticles, in a Luminescent Solar Concentrator Sensitized with Carbon Dots.

Luminescent solar concentrators (LSCs) have become an attractive way to produce green energy via their integration into buildings as photovoltaic windows. Recently, carbon quantum dots (C-QDs) have become the most studied luminescent material for the manufacture of luminescent solar concentrators due to their advantages, such as low toxicity, sustainability, and low cost. Despite the advantages of carbon quantum dots, they remain a low-efficiency material, and it is difficult to fabricate LSCs with a good performance. To address this problem, some of the research has used SiO2 nanoparticles (Nps) to produce a light-scattering effect that helps to improve the system performance. However, these studies are limited and have not been discussed in detail. In this regard, this research work was designed to evaluate the contribution of the scattering effect in different systems of carbon quantum dots used in a possible luminescent solar concentrator. To carry out this study, C-QDs and SiO2 Nps were synthesized by hydrothermal methods and the Stober method, respectively. We used different concentrations of both materials to fabricate film LSCs (10 × 10 cm2). The results show that the light scattered by the SiO2 Nps has a double contribution, in terms of light redirected towards the edges of the window and as a secondary source of excitation for the C-QDs; thus, an improvement in the performance of the LSC is achieved. The best improvement in photoluminescence is achieved when the films are composed of 20% wt carbon quantum dots and 10% wt SiO2 Nps, reaching a gain of 16% of the intensity of the light incident on the edges of the window with respect to the LSCs where only C-QDs were used.

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.

Reducing reabsorption in luminescent solar concentrators with a self-assembling polymer matrix

Reabsorption in luminescent solar concentrators (LSC) is a major factor hindering their commercialisation. This issue is caused by the inherently small Stokes shift of luminophores which creates a large spectral overlap between absorption and emission, leading to reabsorption of waveguided photons. As reabsorption events amplify loss mechanisms such as escape cone losses and non-radiative emission, they are the most detrimental to photon output. Reducing reabsorption can be achieved by decreasing the amount of luminophore-doped waveguide compared to the overall LSC, resulting in an increase in research of both thin film LSCs, and new methods of templating or etching polymer thin films to reduce lateral reabsorption. Here we use self-assembly to alter the structure of a common host matrix, poly (methylmethacrylate) (PMMA) by the addition of a co-polymer, polystyrene-block-poly (acrylic acid) (PS-b-PAA); when in a 1:1 PMMA:PS-b-PAA ratio this creates holes of ~1.6 μm circumference within the polymer matrix, thus providing a simple way to reduce the volume of the luminophore doped host matrix. While quantifying the trade-offs associated with different LSC fabrications and surface effects, we show that the alteration of the host matrix with the PS-b-PAA results in a close to halving of the total number of reabsorption events (PS-b-PAA = 4.4; PMMA = 4.0; 1:1 = 1.8). Device photoluminescence efficiency increases by 10% compared to single component polymer matrices (PS-b-PAA = 76%; PMMA = 77%; 1:1 = 87%), though there is an increase in detrimental outcoupling also linked to this. We also investigated the following polymer ratios of PMMA:PS-b 1:1, 1:2, 1:3, 3:1, 2:1 and found that the ideal ratio to maximise LSC performance is the 1:1 ratio. These trade-offs and new design strategy will aid future efforts in device optimisation.

High efficiency sandwich structure luminescent solar concentrators based on colloidal quantum dots

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.

Absorption coefficient dependent non-linear properties of thin film luminescent solar concentrators

This research article studied absorption coefficient dependent losses and efficiency of thin film luminescent solar concentrator (LSC). The optimum absorption coefficient was determined by fabricating red dye doped thin film LSCs with varying absorption coefficients of 24–202 cm-1. The optical, electrical, and ray-trace model predicted results were compared to establish the optimum absorption coefficient for fabricated thin film LSCs. The optical and electrical efficiencies of thin film LSCs are a function of absorption coefficient; follow linearly at lower values, gradually becoming non- linear at higher values of absorption coefficient which restricts the overall efficiency. The multi layered ray–trace model predicted results deviated from the experimental results at high absorption coefficient. Non-linearity was introduced by losses mechanism of re-absorption, resonant energy transfer (RET), and scattering in thin film LSCs. Re-absorption losses were found to be dependent on optical path-length and absorption coefficient of thin film. They were identified and quantified through locally collected emission and optical path-length in thin film LSCs. Re-absorption losses caused a red shift in emission peak by ≈ 20 nm as the absorption coefficient increased from 24 to 202 cm-1. RET decreased fluorescence life time of dye from 5 ns to 2 ns for the absorption coefficient increased from 24–202 cm-1. These absorption coefficient dependent losses limit the optical and electrical efficiency of thin film LSC devices, and compared with bulk LSC.

Optimal design for extending the lifetime of thin film luminescent solar concentrators

This study is concerned with the enhancement of the molecular, weathering stability of two models of thin film luminescent solar concentrators (LSCs). Two model systems of thin film LSCs had been proposed; the first model consists of a transparent PMMA/SiO2 nanohybrid layer coated on a coumarin doped PMMA substrate. The second model designed as the ordinary configuration in which coumarin dye is dissolved in PMMA/SiO2 nanohybrid layer then coated on a transparent PMMA substrate. The effect of nanosilica concentration on the prepared models was studied by TEM, SEM, DSC, FT-IR, UV–vis absorption and indoor photodegradation test. The obtained results suggested the first model for a durable design of thin film LSC applications specially in hot regions.

Effect of a single open sea air scuba dive on human micro- and macrovascular function

This study is concerned with the enhancement of the molecular, weathering stability of two models of thin film luminescent solar concentrators (LSCs). Two model systems of thin film LSCs had been proposed; the first model consists of a transparent PMMA/SiO2 nanohybrid layer coated on a coumarin doped PMMA substrate. The second model designed as the ordinary configuration in which coumarin dye is dissolved in PMMA/SiO2 nanohybrid layer then coated on a transparent PMMA substrate. The effect of nanosilica concentration on the prepared models was studied by TEM, SEM, DSC, FT-IR, UV–vis absorption and indoor photodegradation test. The obtained results suggested the first model for a durable design of thin film LSC applications specially in hot regions.

Novel crosslinked host matrices based on fluorinated polymers for long-term durability in thin-film luminescent solar concentrators

Polymer-based thin-film luminescent solar concentrators (LSCs) currently rely on poly(methyl-methacrylate) (PMMA) as host matrix material. However, PMMA-based LSCs still suffer from degradation due to the limited photostability of the polymer. In this work, a new crosslinked fluoropolymer-based system is presented as a potential alternative host matrix material for the fabrication of durable polymer-based LSC devices. The new host matrix system is obtained by crosslinking a functional chloro-trifluoro-ethylene-vinyl-ether copolymer with an aliphatic isocyanurate crosslinker. It is shown that efficiency values comparable to those obtained with optimized PMMA-based thin film LSC devices can be reached with the new crosslinked fluoropolymer-based LSC system. In addition, superior long-term operational stability compared to PMMA-based devices can be obtained with the new fluoropolymer-based host matrix, as evidenced by long-term continuous light exposure tests (over 500h) on operating LSC devices. The results of this work demonstrate that crosslinked fluorinated polymers represent a class of promising host matrix materials to achieve environmentally stable LSC devices.

Spectral-based analysis of thin film luminescent solar concentrators

We present a method to evaluate the parameters defining the efficiency of luminescent solar concentrators (LSCs). The light harvesting and self-absorption properties of thin film LSCs on glass substrates are determined by optical spectroscopy and the resulting optical efficiency is consistent with the directly measured photon flux gain.

Luminescent Solar Concentrators

Various planar configurations of the luminescent solar concentrator (LSC) are discussed including the uniformly doped, the stacked plate, the thin film, and the multilayered film LSC. Radiation which is lost from the luminescent plate by falling within the critical angle for total internal reflection is examined in terms of the above configurations. A ten parameter efficiency profile has been developed to better evaluate the collector performance and to allow direct comparison with other photovoltaic devices. A collector efficiency of 3.2% is reported and the feasibility of 8 to 10% efficient devices discussed. Several optical distribution factors have been defined and experimentally evaluated for the luminescent plate and associated photovoltaic cell. These factors have been used to calculate a plate-to-cell optical coupling coefficient for two commercially available solar cells. LSCs based on organic and inorganic phos-phor systems are compared and the problem of dye staility discussed.