# New Light on Phtyoremediation: The Use of Luminescent Solar Concentrators
## 1 Introduction  
In recent years, research for photovoltaics development has been oriented towards the search for lower costs and higher conversion efficiencies. One of the fields of investigation concerns the optimal use of the solar spectrum by means of Luminescent Solar Concentrator (LSC). A typical LSC consists of a sheet of transparent material (generally polymeric matrix as PolyMethylMethylMethylAcrylate (PMMA)) where luminescent particles are homogeneously dispersed. The luminescent particles can selectively absorb the solar radiation and re-emit the energy absorbed at longer wavelengths, where PhotoVoltaic (PV) cells exhibit the highest efficiency. Therefore, the light is captured by the larger, planar surface of the slab,and the main part (-75%) of the converted radiation is waveguided in the slab's plane (thanks to the total internal reflection) and concentrated on the smaller PV cell area on the edges to produce electricity (Figure 1). This reduces the amount of Silicon cells needed to generate a particular amount of energy and the overall cost of the panel, since the waveguiding material is inexpensive. The hypothesis of converting the incident solar spectrum into monochromatic light in the LSCs was already proposed at the end of the 1970s, when LSCs based on organic dyes were first introduced as a low-cost technology to enhance the power conversion efficiency (PCE) of PV solar cells through improving their spectral response [1]. They can collect both diffuse and direct solar radiation, making them a suitable technology to be used in countries where diffuse solar radiation is dominant (more than 50%) such as in northern European countries [2]. Unlike traditional PV panels, LSCs are transparent and can be made with a wide variety of colors and shapes. Thanks to these characteristics, LSCs can be seen as potential structural energy components in the design of PV windows, skylights, and colored PV panels in building facades, but also of noise barriers, advertisement signs, shelters, agricultural covers, and so on, reducing environmental pollution caused by fossil fuels. The considerable energy savings achievable by using LSC panels could also have an interesting application in the field of remediation of contaminated sites. Several different physicochemical and biological approaches have been suggested for the remediation of contaminated water [3; 4; 5] and soils [6; 7], so that selecting a suitable technology is often a difficult yet crucial step for the successful reclamation of a contaminated site [8; 9]. However, activities aimed at the remediation of contaminated sites or the treatment of effluents also have an environmental impact, since they make use of chemical products or processes, with consequent consumption of raw materials and energy. In many cases these aspects are not negligible, and could compromise the sustainability of the approach or even invalidate its beneficial aspects. This is the case with the Electro Kinetic Remediation Technology (EKRT) [10; 11], which has proved particularly interesting and efficient in dealing with various types of contaminations allowing in situ interventions, and demonstrates a more ecological character, compared to other approaches [12], but suffers from some critical issues including high energy consumption [13] that require new solutions to confirm the technology as operationally valid. In light of a growing demand for remediation interventions characterized by high environmental sustainability, there is a considerable request to promote those technologies with a reduced impact on the environment, among which a primary role is attributed to phytoremediation. This term includes a series of technologies based on the use of plants to remediate organic and inorganic contaminants in soil and other environmental matrices  
Figure 1: Diagram of incident photons and photons emitted by a dye molecule inside the Luminescent Solar Concentrator (LSC). (sediments, water).