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In order to improve the utilization rate of solar energy, a new type of photo-thermal phase-change microcapsules PCM@SA@PDA was successfully prepared with n-docosane (C-22) as core material and sodium alginate (SA) and polydopamine (PDA) as composite wall material. Here, SA capsules were formed by cross-linking of metal ions to envelop and prevent the leakage of melted C-22 (PCM@SA). Dopamine was self-polymerized on the surface of PCM@SA microcapsule; thus, efficient light absorption was achieved for photo-thermal transformation. The chemical structure, thermal properties, light absorption properties and photo-thermal conversion properties of the prepared microcapsules were analyzed and characterized. Based on the study of the effect of different contents of C-22 core materials on the thermal storage performance of PCM@SA, the optimal addition amount of C-22 was determined to prepare photo-thermal phase-change microcapsules. Compared with the PCM@SA, the photo-thermal phase-change microcapsule PCM@SA@PDA still showed good stability and heat storage performance. Their melting heat enthalpy was about 152.5 J g−1, and they also showed better photo-thermal conversion performance. Combining C-22, SA and PDA to prepare photo-thermal conversion phase change energy storage materials, the method was characterized by strong adaptability, simple operation, low production cost and high economic benefits, which could not only further improve the stability of the composite material, but also increase the photo-thermal conversion efficiency of the system. Therefore, this composite material integrating active light absorption, conversion and storage functions would have higher solar energy utilization rate and broader application prospect. [ABSTRACT FROM AUTHOR]