Epoxy-Silicon Composite Materials from End-of-Life Photovoltaic Panels

Waste and Biomass Valorization https://doi.org/10.1007/s12649-023-02135-2 ORIGINAL PAPER Epoxy‑Silicon Composite Materials from End‑of‑Life Photovoltaic Panels C. Pavlopoulos1 · A. Christoula1 · A. C. Patsidis3 · D. Semitekolos1 · K. Papadopoulou1 L. Zoumpoulakis1 · G. Lyberatos1,2 · G. C. Psarras3 · Received: 14 November 2022 / Accepted: 2 April 2023 © The Author(s) 2023 Abstract The prospect of using recovered solar cells from end-of-life (EoL) photovoltaic panels (PVPs) to produce composite materials with dielectric properties was studied. The main goal of this research was to reduce the waste originating from EoL PVPs by reusing the semiconductor, thus rendering solar energy an even greener energy source. Solar cells were recovered from EoL PVPs through thermal treatment to remove polymer sheets and screening to separate the solar cells from glass and electrodes. Composite materials were manufactured by reinforcing two different epoxy resins, Araldite LY556 and Resoltech 1050, with varying concentrations of ground solar cells (0–10% w/w). The mechanical and dielectric properties of the composite materials were examined with bending and shearing tests and Broadband Dielectric Spectroscopy (BDS), respectively. The responses from the two different resin matrices were compared. It was found that the produced composite material resulting from Resoltech resin reinforced with solar cells recovered from EoL PVPs had better mechanical and dielectric properties. BDS characterization of the composite materials indicated that the solar cells can be used to enhance the energy storage capacity of the polymeric matrix and thus may be potentially used in the manufacturing of capacitors. Graphical Abstract Keywords Photovoltaic panels · Silicon · Epoxy composite · Composite materials · Dielectric · Solar cells Statement of Novelty * K. Papadopoulou 1 School of Chemical Engineering, National Technical University of Athens, Athens, Greece 2 Institute of Chemical Engineering Sciences (ICE-HT), Stadiou Str, 26504 PlataniPatras, Greece 3 Department of Materials Science, School of Natural Sciences, University of Patras, 26504 Patras, Greece A significant increase in waste originating from end-of-life photovoltaic panels is expected in the upcoming decades, as the world is turning to renewable energy sources. Therefore, a sustainable management plan for recovering and reusing critical materials in photovoltaic panels becomes imperative. Researchers, so far, have focused mainly on material recovery. This study approached the recyclability issue by focusing on utilization of crystalline silicon contained recovered from first generation solar cells and the possibility of 13 Vol.:(0123456789) Waste and Biomass Valorization reusing the material for electronic applications in the form of composites. Silicon was recovered and used as filler particle, successfully enhancing the dielectric properties of polymeric matrices, while preserving the simplicity of the whole process, demonstrating that it can be reused for energy storage applications. Introduction In the recent years, energy production through renewable sources has become increasingly competitive in terms of cost and imperative in terms of carbon footprint. One of the dominant renewable energy sources is solar radiation which may be harvested through solar photovoltaic panels (PVPs). By the end of 2015, installed solar PVPs reached a capacity of 200 gigawatts (GW) and it has been estimated to increase to 4500 GW globally by 2050. Since photovoltaic panels have a life span of about 25–30 years, it is expected that in the next decade thousands of metric tons of installed photovoltaic panels will be withdrawn from existing parks as waste. Their potential disposal in landfills will lead to loss of critical and valuable materials that can potentially be reused [1–3]. Characterization of this upcoming type of Waste from Electrical and Electronic Equipment (WEEE) has concerned researchers globally, who investigate possible environmental and economic impacts of solar PVPs after their end of life (EoL) [3–5]. Researchers have focused on material recovery from 1st generation EoL solar PVPs that use monocrystalline and polycrystalline silicon as semiconductor since the beginning of the century. Physical and/or thermal treatment processes have surpassed chemical methods, as avoiding the use of organic solvents to dissolve the polymer sheets in the PVPs is more sustainable, both economically and environmentally [2, 6]. In a previous work, an integrated hydrometallurgical process for the recovery of pure crystalline Si and Ag from end of EoL Si PVPs has been proposed [7]. The high temperature required for the manufacturing of crystalline silicon solar cells renders it a valuable material to be recovered and reused, despite its vast availability in nature. Research on material recovery and recycling from EoL PVPs is extensive [4–9], whereas reports on alternative utilization of recovered materials are limited [10]. In a previous work, a potential reuse pathway of first generation PVP waste as aggregate in Portland cement was studied [11]. However gas formation in the cement paste led to decreased performance for the case of silicon PVPs. Researchers have used silicon or silica based materials to enhance the dielectric properties of polymeric matrices such as epoxy resins [12–15]. So, in the present study, an alternative valorization of silicon’s semiconductor properties is evaluated, by reusing the recovered silicon from end 13 of life PVPs as an additive in a polymer matrix, aiming to produce a material for energy storage applications while providing a sustainable reuse pathway for EoL crystalline silicon PVPs. Polymers and polymer matrix composites are electric insulators and have dielectric characteristics. With the application of an external field, their electrical response is primarily related to relaxation phenomena, which describe the delay of a physical system to follow an externally applied excitation. The observed relaxation processes are strongly influenced by the positioning of the polymer chains and the existence of polar groups. External factors such as additives also affect dielectric properties. It has been proven that the concentration of conductive inclusions is a critical parameter governing the electrical behaviour of composite materials [16, 17]. Bisphenol resins are commonly used as a matrix for composite materials and have been greatly studied for the relaxation phenomena that appear when exposed to external electrical fields [18–20]. The separation of the positive from the negative charges throughout the volume of the material creates an overall polarization in it. The latter can be distinguished into deformation polarization from the intramolecular displacements, orientation polarization from the permanent dipoles in the material, and interfacial polarization [16]. As the systems in this study are heterog (...truncated)