Graphene Microflower by Photothermal Marangoni-Induced Fluid Instability for Omnidirectional Broadband Photothermal Conversion
Kun Tian, Xupeng Fan, Si Cheng, Qing Zhu, Shuai Zheng, Qi Sun, Liwei Zhao, Ye Li, Miaomiao Zhang, Huikang Xu, Chunyan Qu, Dezhi Wang, Chengyang Wang, Changwei Liu, Dianpeng Qi
Abstract
2-D carbon-based materials are well-known for their broadband absorption properties for efficient solar energy conversion. However, their high reflectivity poses a challenge for achieving efficient omnidirectional light absorption. Inspired by the multilevel structures of the flower, a Graphene Microflower (GM) material with gradient refractive index surface was fabricated on polymer substrates using the UV-intense laser-induced phase explosion technique under the synergistic design of the photothermal Marangoni effect and the fluid instability principle. The refractive index gradient reduces light reflection and absorbs at least 96% of light at incident angles of 0–60° across the entire solar wavelength range (200–2500 nm). Over 90% absorption even at 75° angle of incidence. The light absorption is enhanced by the multiple interferometric phase cancelation and localized surface plasmon resonance, resulting in a steady-state temperature 60 °C higher than ambient conditions under one solar irradiation. The max rate of temperature rise can reach up to 62 °C s –1 . The device is then integrated at the hot end of the temperature difference generator at high altitude to ensure continuous and efficient power generation, producing a steady-state power of 196 mW.