Effects of a coating combination, a prism film and a phosphor layer on the short current of the solar cell in the optical solar concentrator and the illuminance of the sunlight passing through the samples were investigated. The optical solar concentrator was a 50 mm x 50 mm x 5 mm B270 thick glass with its sides connected by a solar cell. The prismatic structure of the prism film had a period of 50 μm. A phosphor Y560 having an absorption band of 390 nm to 500 nm and emitting from 490 nm to 700 nm was prepared. Six coating combinations applied in this study were composed of optical filters and glass. The optical filters included infrared cut-off, magenta, red, green and blue filters. The deflection angle was between 31 and 33 degrees when the incident sunlight passed through the prism film. The short current of the solar cell in the optical solar concentrator with the prism film, the coating combination and the phosphor layer was largest in this study. Experimental results show that the coating is more suitable for enhancing the short current than the phosphor layer in the optical solar concentrator with the prism film. And the phosphor layer can increase the illuminance of the sunlight passing through the samples due to the human eye sensitivity.
The reabsorbing effect will prevent the receiving energy for the solar cell attached to the edge of a luminescent solar concentrator from increasing with the illuminated area. The conventional solar concentrator adopts a uniform luminescent layer made of only one type of phosphor or dye. When the light generated in the region of the luminescent layer far away from the solar cell propagates to the solar cell by multiple total internal reflections, it will have more chances to be reabsorbed when it enters the region of the luminescent layer near to the solar cell. We investigate how the reabsorption effect can be reduced by using a luminescent layer made of multiple phosphors such that the region with the phosphor absorbing the longer wavelength is arranged to cover the region nearer to the solar cell. Experimental results show that the proper coverage with multiple phosphors can reduce the reabsorption effect in our luminescent solar concentrator under test.
As an application of the PV technology, building integrated photovoltaic (BIPV) technologies have attracted an increasing interest in the past decade. One of these BIPV elements is the luminescent solar concentrators (LSCs). The LSC consists of a transparent plate embedded with luminescent dyes or inorganic particles, and the solar cells are attached on one or more sides. The incoming sunlight absorbed by the luminescent dyes or inorganic particles re-emits at a longer wavelength, and part of the re-emitting light trapped in the transparent plate reaches the PV cell attached on the LSC and convert it to electricity. However, the efficiency of the LSCs is still low at this stage. The surface loss on the top surface of the transparent plate is one of the main losses in LSCs. The prism film in liquid-crystal display (LCD) module is used to collimate the light in the module and enhance the overall brightness, and would be used in the LSCs to enhance the incoming sunlight to the solar cells attached on the end of the transparent plate. Then the design of the prism film is important. In this study, the ray-tracing simulation is used to investigate the optical characteristics of the LSC with the prism film covered on the top surface of the transparent plate. Different structure of the prism film will be considered to enhance the light reaches the PV cell attached on the LSC.
In this paper, the luminescent solar concentrator comprises a thick glass with a spectrally-selective optical coating deposited on the bottom surface and an inorganic phosphor layer contacted on the coating surface. A solar cell is contacted to the lateral surface of the thick glass. Spectrally-selective coatings are applied to reflect and redirect the invisible solar radiation to the edges of luminescent solar concentrators. These coatings also transmit the visible solar light and the emission light of the inorganic phosphor. The short-circuit current of the solar cell is measured in a flashing-mode solar simulator with metal-dielectric heat mirrors and dielectric edge filters coated on the thick glass of the luminescent solar concentrators respectively. Experimental results show that the dielectric edge filter will increase the short-circuit current of the solar cell and the invisible light falling on the solar cell in our luminescent solar concentrator. The metal-dielectric coatings, silver-based transparent heat mirrors, will not increase the short-circuit current of the solar cell in our luminescent solar concentrator due to absorption of metal films.
The Luminescent Solar Concentrator (LSC) consists of a transparent plate with solar cells on one or more sides. The incoming sunlight is absorbed by the luminescent dyes or particles, which are embedded in the transparent plate or applied in a film on the top or bottom of the transparent plate. The absorbed light is re-emitted at a longer wavelength, and part of the re-emitting light is trapped in the transparent plate by total internal reflection (TIR). Then the solar cells attached to the edges of the transparent plate would collect the light and convert it to electricity. However, the luminescent dyes or particles used in the conventional LSC still suffer from reduced efficiencies and lifetimes, then the inorganic phosphors with relatively high quantum yields, good absorption properties and longer lifetime could be alternative materials used in the structure. In this study, the ray-tracing simulation is used to investigate the optical characteristics of the LSC with the inorganic phosphors embedded film on the top or bottom of the transparent plate. The simulation results will also be used to study the loss mechanisms in the LSC with inorganic phosphors embedded film.