###### Abstract  
Organic phase change materials (PCMs) have been widely studied for thermal management applications, such as the passive cooling of silicon photovoltaic (PV) cells, whose efficiency is negatively affected by rising temperature. The aim of the present study is to investigate the shape stabilization of PCMs by using expanded graphite (EG) as a highly conductive supporting matrix, leading to the development of novel PCM/EG composites with melting temperatures in the range 30-50 \({}^{\circ}\)C. Different organic PCMs were selected and compared, i.e., two paraffins and a eutectic mixture of fatty acids (myristic and palmitic acid). The EG was vacuum-impregnated with organic PCMs, and, subsequently, powdery composites were cold-compacted to obtain dense heat-absorbing panels. The thermal conductivity was enhanced up to 6 W/m\(\cdot\)K, guaranteeing composites with a melting enthalpy of 160 to 220 J/g. This study found that the EG vacuum impregnation method is suitable for PCM shape stabilization, and cold compaction allows for the formation of solid panels with improved thermal response. The obtained PCM/EG composites were utilized to produce panels of about 6 \(\times\) 6 \(\times\) 2 cm\({}^{3}\), suitable for the thermal management of silicon PV. P 202  
advantages offered by silicon technology such as their low-cost, environmental friendliness, and economies of scale [5]. PV cells absorb part of the incoming energy from the sun, dissipating the rest into heat. The excessive heat can raise module temperatures, shortening their lifespan and reducing their efficiency. In particular, the conversion efficiency of crystalline silicon solar cells decreases by 0.3-0.5% for every degree of temperature increase. Silicon solar cell efficiencies are approaching the maximum theoretical value [6]; hence, thermal management becomes fundamental to minimize efficiency losses. It is therefore essential to maintain the lowest possible working temperatures, developing active or passive cooling systems to be coupled with PV cells [7; 8]. Because active cooling requires specifically dedicated energy consumption, passive systems are energetically preferred [9; 10]. An emerging strategy in the field of passive cooling is the use of phase change materials (PCMs), storage materials able to absorb incoming heat flux during melting and store it in the latent form at constant temperature. The stored latent heat is released in crystallization during the opposite thermal cycle, as reviewed in the literature [11; 12]. PCMs have been exploited in many applications related to energetic transition. They may replace insulating materials to mitigate building environmental impacts [13], and also, they can prevent overheating in electronic devices [14] and batteries [15; 16]. In addition, they have been proposed for low-temperature thermal energy storage (TES) [17; 18]. PCMs can also be employed in PV modules as passive cooling systems to mitigate the already mentioned efficiency losses [19; 20; 21; 22]. PCMs are subdivided into classes based on their chemical structure: organic, inorganic, and eutectic mixtures [23]. Organic PCMs include paraffins, fatty acids, and poly(ethylene glycol) derivatives. They offer advantages such as high melting enthalpy, non-corrosiveness, chemical stability, and no supercooling phenomenon. However, they present high volumetric expansion upon melting, flammability, and low thermal conductivity. These drawbacks do not exist in inorganic PCMs, a class composed of salts, hydrated salts, metals, and alloys. Nevertheless, inorganic PCMs are often avoided because they are corrosive, scarcely stable, and they may incur the supercooling phenomenon. Likewise, eutectic mixtures are combinations of two or more PCMs of the previous classes, which enable the fine-tuning of PCM melting temperatures. Because of their disadvantages, inorganic PCMs are discarded, and in the following, we consider only organic PCMs and their eutectic mixtures.