UV-LIG-Based Perfect Broadband Absorber for Solar Thermoelectric Generation

Thermoelectric technology is gaining paramount importance for solar energy conversion and electricity production to increase green energy resources with high efficiency. An enormous amount of research is being carried out for engineering various solar absorbers using tailored materials and structures for solar energy harvesting. However, the methods to achieve cost-effective light absorbers are still challenging. Here we present a perfect broadband solar absorber for efficient photothermal conversion of sunlight employing a low-cost ultraviolet laser-induced graphene (UV-LIG) prepared on a polymer material using the conventional direct laser writing method. Recently the LIG generation employing the direct laser writing method has been recognized as a straightforward and low-cost technique to generate graphene foam. We have patterned the UV-LIG to produce a two-dimensional grid pattern to limit the reflection losses. The resulting UV-LIG surface exhibits very high absorption (>99%) for the entire spectral range of sunlight. Significantly, the absorber attains a temperature of 90.4 °C under 1 sun irradiation within a response time of less than 60 s. Further, we have exploited the extraordinary photothermal property of the patterned UV-LIG together with a commercially available thermoelectric generator (TEG) to make a solar thermoelectric generator (STEG) device with excellent output performance. Our investigation perceived that the structured UV-LIG absorber-based STEG has excellent power generation capability compared to the STEGs with other absorbing materials. Remarkably, we could achieve an output voltage of 273.9 mV under 1 sun irradiation, one of the highest among the recent STEGs, primarily due to the enhanced absorption of absorbing material. These results suggest that the proposed versatile and robust solar energy harvesting technology can be employed for solar–thermoelectric conversion systems.