Latent thermal energy storage using phase change material (PCM) is an effective way to store and transport thermal energy. In this work, a shape-stabilized light-to-thermal conversion composite PCM containing 72.5 wt% CH₃COONa·3H₂O (SAT), 0.4 wt% Na₂HPO₄, 17.1 wt% expanded graphite (EG) and 10 wt% CuS was prepared using a physical blending and impregnation method. Experimental results showed that Na₂HPO₄ was an effective nucleating agent, greatly promoting SAT crystallization. EG as supporting material played an important role in preventing melting PCM from leakage. The addition of CuS can increase the light-to-thermal conversion efficiency from 66.9% to 94.1%. The resultant composite PCM had high phase change enthalpy of 194.8 J/g, low supercooling temperature and good thermal cycling performance. After 150 thermal cycles, the melting enthalpy and light-to-thermal conversion efficiency were decreased by only 5.9% and 2.6%, respectively. This material could be suggested as a potential candidate for storage of thermal energy in solar energy utilization.