Biochar-based phase change materials (PCMs) are suitable for energy conservation to regulate the environment of greenhouses, but would benefit from higher specific surface area biochar to increase the polyethylene glycol (PEG) loading and enhanced thermal conductivity to promote efficient heat transfer. Moreover, since solar radiation is not constant for photo-thermal conversion, a material with an additional energy conversion process, e.g. electro-thermal conversion, would be advantageous. Herein, maize straw-derived activated porous biochar nanosheets were prepared and impregnated with PEG to afford PCMs. Due to their high specific surface area, the PEG loading capacity in the biochar nanosheets reaches 88.9%, with no leakage observed during phase transitions. The latent heat and photothermal conversion efficiency of the materials increase with the loading content of PEG. Hierarchical porous structures in the biochar nanosheets endow the material with a high thermal conductivity exceeding 0.585 W m(-1) k(-1). In addition, electro-thermal conversion of the materials was achieved due to increased graphitization of the biochar nanosheets. The electrical conductivity and electro-thermal conversion efficiency decrease with the loading content of PEG. The material with 85.7% PEG content is the most favorable in terms of thermal conductivity as well as light- and electro-driven phase change behaviors.