Abstract: The present invention relates to an encapsulant capable of reducing potential-induced degradation (PID). The encapsulant is used to seal a solar cell to form a photovoltaic module, in which silica gel is dispersed in the encapsulant as a sodium ion adsorbent. Since the silica gel that is highly transparent is used as the sodium ion adsorbent, it is possible to prevent PID attributable to sodium ions and to prevent deterioration in photovoltaic efficiency of the photovoltaic module. Since the silica gel has a high specific surface area, it is possible to adsorb sodium ions with a small amount of the silica gel.