Interfacial solar seawater desalination, originating from the driving force of the conversion of sunlight into heat energy, has been facing the negative influence of intermittent solar radiation alternating between night and day. Here, a novel Janus-type hybrid metamaterial is proposed to prolong "the number of hours of sunshine" for efficient solar-thermal vaporization effect based on the surplus solar-generated heat input/output across the reversible solid-liquid phase transition from phase change materials (PCMs). The coaxial fiber membrane with PCM-loaded core-sheath structure is one of the most key materials of the hybrid metamaterial to extend the sunshine duration. The two layers of the Janus-type hybrid metamaterial presented the following characteristics: one side had a fast solar-thermal conversion, in situ heat storage ability, and the other had predominantly low thermal conductivity against thermal loss and good hydrophilicity for seawater absorption. Impressively, the exploiting metamaterial demonstrates a high solar thermic vaporization efficiency of 85.7% and a stable freshwater yield of 1.62 kg m(-2) h(-1) under 1 sun exposure. More importantly, the Janus-type hybrid metamaterial still exhibits an additional conversion efficiency of 8% attributed to surplus solar-generated heat output even without sunlight. Therefore, such a Janus-type hybrid metamaterial can provide a promising path for higher efficient solar-to-heat utilization.