Solar　water　evaporation　is　a　sustainable　and　efficient　way　to　produce　fresh　water.　Identifying　highly　efficient　photothermal　materials　is　an　important　step　for　achieving　high　evaporation　rates.　However,　the　effects　of　the　water　interfacial　area　are　rarely　paid　any　attention,　although　a　few　reports　have　demonstrated　high　evaporation　rates　from　micro-/nanostructured　devices.　In　this　work,　we　introduce　a　new　term,　water　mass　per　unit　surface　area　(WMUA),　to　connect　the　water　mass　and　interfacial　area.　We　can　regulate　WMUA　using　different　commercial　porous　materials　to　realize　water　management　in　devices,　which　further　affects　the　evaporation　rates.　The　optimized　device　is　composed　of　suedette　sponge,　filter　paper,　and　polydopamine　as　the　water-transportation,　water-restrictive,　and　photothermal　materials,　respectively,　and　it　achieves　an　evaporation　rate　of　1.8　kg　m−2h−1and　energy　efficiency　of　∼92%.　This　presents　a　new　strategy　for　the　rational　design　of　device　structures　and　the　promotion　of　evaporation　rates,　pushing　this　field　into　new　areas.　©　The　Royal　Society　of　Chemistry　2021.