The application of luminescent down-shifting (LDS) has been shown to improve the short wavelength response of a variety of different photovoltaic devices. Cadmium sulphide/cadmium telluride ...(CdS/CdTe) heterojunction devices possess a great potential for improvement via LDS due to the parasitic absorption of blue light by the CdS buffer layer. This work is the first to investigate LDS applied to mini-modules (72cm2 active area) cut from full-size CdTe modules from a production line. The addition of LDS layers containing Lumogen Yellow 083 and Violet 570 dyes was demonstrated to increase the short circuit current density (JSC) of the mini-module by up to 9% relative. It was shown that the addition of the Yellow 083 dye alone more than doubles the short wavelength (300–500nm) response of CdTe mini-modules. External quantum efficiency measurements are presented that clearly identified the wavelength range of photocurrent enhancement, while increased efficiency was confirmed with current–voltage (I–V) measurements.
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► Thin PMMA layers were doped with Lumogen V570 and Y083 luminescent dyes. ► These layers were applied to CdTe spot cells (1.13cm2) and mini-modules (72cm2). ► Mini-module JSC increased by 9% with the layer doped with V570 and Y083 dyes. ► Mini-module JSC from 300 to 500nm photons doubled for all layers containing Y083.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Ultrathin crystalline silicon (c-Si) solar cells represent an important technology development direction for reducing material usage and thus lowering the cost of solar electricity. Here, we ...demonstrate a prototype device with high efficiency assisted by a micro-/nano-structured polycarbonate thin nanofur film inspired by water ferns. The ultrathin c-Si solar cells consist of a 17 μm-thick c-Si absorber and exhibit an efficiency of up to 17.3% and short-circuit current density (Jsc) of 35.8 mA cm−2. With the assistance of the thin nanofur, the efficiency is increased to 18.1% due to an increase in Jsc to 37.4 mA cm−2. The photocurrent enhancement is attributed to, firstly, a more favorable refractive index transition due to the polymer addition and, secondly, the high forward scattering of the structured film, which increases the optical pathlength within the ultrathin absorber layer of the devices. To our knowledge, the present prototype device demonstrates the highest Jsc and efficiency in the area of ultrathin c-Si solar cells with an absorber layer of less than 20 µm.
•17 μm-thick ultrathin crystalline Si solar cell fabricated with 18.1% efficiency.•Photocurrent enhancement of 1.6 mA cm−2 realised via bioinspired polymeric “nanofur”.•An absolute efficiency improvement of Δη = 0.8% is achieved.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Luminescent materials suitably embedded into the architecture of photovoltaic (PV) modules can increase the short-wavelength response and, thus efficiency, of nearly all in-production PV ...technologies. At the same time, visible-wavelength luminescence that escapes the modules due to its omnidirectional nature is perceived as color when it reaches the human eye. It is shown that this "lost" luminescence can be used for the application of aesthetical as well as functional coloration, while maintaining-or even increasing in favorable cases-the efficiency of commercial PV modules. Cadmium telluride (CdTe) and crystalline silicon (c-Si) minimodules were encapsulated with luminescent add-on layers. Performance enhancement of 0.4 mA/cm 2 is reported as the best result for a CdTe minimodule with a custom graphical design. Results on c-Si devices indicate that it is possible to use graphic designs, leading to only a small reduction in electrical output. Aspects and implications arising from the potential for aesthetical and functional coloration of commercial PV modules are discussed, together with technical challenges that need to be addressed.
Development of self-cleaning coatings is of great interest for the photovoltaic (PV) industry, as soiling of the modules can significantly reduce their electrical output and increase operational ...costs. We fabricated flexible polymeric films with novel disordered microcavity array (MCA) topography from fluorinated ethylene propylene (FEP) by hot embossing. Because of their superhydrophobicity with water contact angles above 150° and roll-off angles below 5°, the films possess self-cleaning properties over a wide range of tilt angles, starting at 10°, and contaminant sizes (30–900 μm). Droplets that impact the FEP MCA surface with velocities of the same order of magnitude as that of rain bounce off the surface without impairing its wetting properties. Additionally, the disordered MCA topography of the films enhances the performance of PV devices by improving light incoupling. Optical coupling of the FEP MCA films to a glass-encapsulated multicrystalline silicon solar cell results in 4.6% enhancement of the electrical output compared to that of an uncoated device.
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IJS, KILJ, NUK, PNG, UL, UM
The irradiance concentrated along the edges of a planar luminescent solar concentrator (LSC) is not uniform across their length. This geometrical effect results in a deviation of up to 40% between ...the extreme ends and the middle of an edge for a large-area LSC. Consequently, the typically in-series interconnected solar cells attached to the edges of the LSC are not illuminated equally resulting to current mismatch. It is shown that by reducing the lengths of the more central solar cells so that current matching is achieved, more cells can be attached to each edge. This way, the voltage and power output of the string can be increased. In this work, a 60 cm × 60 cm × 0.3 cm LSC with 26 solar cells mounted to its edges was constructed and characterized. These dimensions result in geometrical concentration of 50×, while the LSC exhibited average irradiance concentration of 4.8×. An increase of 15% in power output and efficiency is demonstrated via the reduction of the length of central cells, current matching, and the consequent connection of one more cell to the string of an edge. A solar-to-electric power conversion efficiency of 1.55% is reported for the large-area LSC module.
In this work we report on the coloring of perovskite solar cells (PSC) by combining the ease of freedom in design of the solar cell’s shape with the bright color of luminescent down-shifting (LDS) ...layers. Both the perovskite solar cell and the LDS layers are fabricated with digital inkjet-printing processes, such that the perceived color of the devices can be tuned independently from the shape of the device. The results demonstrate that a strong color perception of the PSCs with the use of luminescent materials of various colors can be achieved at a relatively small (∼17%) reduction of power conversion efficiency.
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IJS, KILJ, NUK, PNG, UL, UM
Luminescent materials suitably embedded into the architecture of photovoltaic (PV) modules can increase the short-wavelength response, and thus efficiency, of nearly all inproduction PV technologies. ...At the same time, visible-wavelength luminescence that escapes the modules due to its omnidirectional nature is perceived as color when it reaches the human eye. It is shown that this "lost" luminescence can be used for the application of aesthetical as well as functional coloration, while maintaining or even increasing in favorable cases the efficiency of commercial PV modules. Performance enhancement of 0.4 mA/cm 2 is reported for a CdTe mini-module with a custom graphical design.
Luminescent down-shifting (LDS) performance is presented for different production-line cadmium telluride (CdTe) mini-modules manufactured in 2009 (CX1) and 2012 (CX3). The 10 cm × 10 cm mini-modules ...were laminated with LDS layers that consist of luminescent organic dye-doped ethylene vinyl acetate (EVA) and a fluorinated ethylene propylene (FEP) cover sheet. The external quantum efficiency of the devices was measured before and after the encapsulation. All LDS layers improved the short-circuit current. Lumogen Yellow 083 (Y083) and 170 (Y170) dyes showed the greatest relative improvement in the short-circuit current for the CX1 devices (9.6% and 9.7%, respectively), while Lumogen Yellow 083 showed the largest improvement for the CX3 (5.3%). The different vintages of modules also enabled an investigation of how the enhancement possible with LDS relates to other technological efficiency improvements for CdTe cells and indicates the level of future improvements possible. Finally, initial results of the same EVA-FEP LDS layers that contain the V570, Y083, and mixture of the two dyes are also presented for full-size (120 cm × 60 cm) CX3 production line modules (2012). The full-size module results indicate that scale up of the method is feasible with the Y083 layer, which improves short-circuit current by 4.3%.
Luminescent down shifting (LDS) is a light management technique that can be used to exploit more efficiently the short-wavelength photons of the solar spectrum, to which most solar cell technologies ...exhibit relatively poor response. In practice, LDS is a thermalization process of carriers that takes place outside the solar cell itself and, therefore, has the potential of reducing its operating temperature, and thus increasing its electrical power output in field applications. In this study, we use ray-tracing and an electric-like thermal circuit to calculate the temperature variation of both multicrystalline silicon (mc-Si) and cadmium telluride (CdTe) photovoltaic modules containing LDS layers. We find that the dominant factors for the final operating cell temperature under the modified spectrum are reduced light reflection and parasitic absorption in the encapsulants. LDS, in practice, results in only a small variation compared with standard non-LDS modules, of up to +0.1 °C for the case of mc-Si and -0.6 °C for the CdTe. Although lowering operating cell temperature by means of LDS does not constitute in itself a strong reason for adopting the technology, this study paves the way for using optically active encapsulation layers with this purpose in mind.
This thesis investigates the technology of luminescent down-shifting (LDS) of light for improving the short-wavelength response and efficiency of photovoltaic (PV) modules. A critical literature ...review of previously published work is presented identifying the opportunity to include the luminescent species in the encapsulation layer of certain PV technologies. A range of luminescent materials and mixtures thereof were tested in ethylene vinyl acetate (EVA) host. They all exhibited very high luminescent efficiencies and did not impair the transmittance of the encapsulant. LDS EVA sheets were used to encapsulate multi-crystalline silicon (mc-Si) and chalcopyrite (CIGS) solar cells. An increase in short-λ external quantum efficiency of up to 25 % was achieved for mc-Si devices. For CIGS, the increase was up to 25 % and 40 % for 50-nm- and 100-nm-thick buffers respectively. The overall efficiency of mc-Si devices was improved by 0.2 % in the best case and gains of up to 0.2 mA / cm2 and 0.6 mA / cm2 were achieved for 50-nm- and 100-nm-thick buffer CIGS devices. LDS offers the additional benefit of device colouration, which can encourage the further uptake of PV in applications where colour is a desirable property.
