Date/Time: 04-23-2019 - Tuesday - 05:00 PM - 07:00 PM
Yang Li1 Chongjia Lin1 Baoling Huang1

1, The Hong Kong University of Science and Technology, Kowloon, , Hong Kong

Solar thermophotovoltaic (STPV) systems, which leverage the benefits of both solar-thermal and photovoltaic (PV) technologies, involve efficient and dispatchable approaches to generating electricity. The key components in a STPV system include a selective solar absorber, a selective emitter, and a solar cell at least. The total input power of a SPTV system is determined by the sunlight absorption efficiency of the selective absorber. Considering the high operating temperatures of STPV systems, selective absorbers are required to maintain high absorption for solar radiation and low emission beyond a cut-off wavelength in the infrared region to avoid thermal re-radiation even at elevated temperatures. To date, almost all the state-of-the-art selective absorbers/emitters such as cermets and photonic crystals with superior performance (i.e., high selectivity and great thermal stability) were generally manufactured with complicated and expensive micro-fabrication or nano-fabrication techniques, leading to high cost and challenges for large-scale production. Moreover, the obtained absorbers/emitters often encounter problems when being integrated with solution-processed solar cells. Therefore, developing high-performance solution-processed absorbers/emitters is urgently demanded.
Titanium nitride (TiN), as an emerging plasmonic ceramic material, offers tunable plasmonic properties, as well as great thermal and chemical stability. TiN nanoparticles have been proven to show stronger optical losses in the visible range compared to traditional metallic plasmonic materials. In this work, we took advantage of well-dispersed colloidal TiN nanoparticles (20-80 nm) to serve as the absorptive medium for sunlight. The absorption bandwidth, i.e., the cut-off wavelength, can be tuned through rationally controlling the concentration of the TiN colloid and the coating speed. The excited plasmonic resonance of TiN nanoparticles resulted in highly selective absorption of sunlight near their resonance wavelengths. Due to the in-plane plasmonic coupling of adjacent TiN nanoparticles, the resonance wavelength was able to red-shift to near-infrared (NIR) range. As a result, selective sunlight absorption can be attained in the UV-visible-NIR range below the cut-off wavelength. An amorphous SiOx layer, prepared by spin coating a perhydropolysilazane (PHPS) solution, acted as the protection and anti-reflection coating. Both full-spectrum sunlight absorption and strong IR reflection were achieved simultaneously when coated on various IR reflectors, including Au, stainless steel, Al, and TiN. Particularly, the absorbers with Au reflectors exhibited a high solar absorptance of 92.1% and an ultra-low IR emittance of 10.5% at an elevated temperature of 1000 K, producing a solar-thermal energy conversion efficiency of 86.1% under 100 suns. To the best of our knowledge, this performance surpasses or equals those of state-of-the-art selective absorbers fabricated by micro and nano-fabrication techniques. The superior performance of such low-cost solution-processed solar absorbers will potentially put the steps of cost-effective and large-scale STPV systems forward.

Meeting Program