Summary The preparation of phase change materials (PCMs) with high energy storage, thermal conductivity, and photothermal conversion capability is essential for improving solar energy conversion and storage. In this study, graphene oxide (GO) was incorporated into polyurethane (PU) prepared from 4,4′‐diphenylmethane diissyanate (MDI) and polyethylene glycol (PEG). PU/GO composite PCMs exhibit enhanced thermal conductivity (0.972Wm−1 K−1) because the isocyanate in MDI can covalently graft with GO. The composite solid–solid PCMs has outstanding stability and thermal reliability. It can stay stable at 80°C for more than 15 min without leaking and has good thermoregulation regulation performance. The thermal energy storage density and photothermal conversion efficiency of PU/GO increase as the amount of PEG and GO increases. The PU/GO composite with 89 wt% PEG and 1.72 wt% GO has a phase change enthalpy of 150.7 J/g and a high photothermal conversion efficiency (95.3%). The composite PU/GO solid–solid PCMs have great potentials for effective energy storage and solar energy utilization.

A series of polyurethane/graphene oxide (PU/GO) solid–solid phase change materials (SSPCMs) were synthesized by using GO as a light-absorbing filler and polyethylene glycol (PEG) as a phase change matrix. The effects of PEG content on the energy storage capacity, thermal stability and photo–thermal conversion performance of PU were investigated. The results show that the form-stability of PU/GO decreases while the phase change enthalpy and photo–thermal conversion efficiency of PU/GO increases with the increasing PEG content. The introduction of a very low content of GO can maintain comparable energy storage density and greatly improve light absorption by reasonably modulating the soft segment contents. The PU/GO composite with 92 wt% PEG has a phase change enthalpy of 138.12 J/g and a high photo–thermal conversion efficiency (87.6%). The composite solid–solid PCMs have great potential for effective energy storage and solar energy utilization.