Efficient broadband solar absorber and thermal emitter based on Ti and InAs with pyramid-like structure

This paper innovatively proposes a broadband solar absorber and thermal emitter with dual-function integration, achieving breakthroughs in the fields of photothermal conversion and high-temperature thermal emission through three core innovations. First, it integrates high-temperature-resistant metal titanium (Ti) and semiconductor indium arsenide (InAs) into a gradient-like pyramid structure for the first time—this design breaks the limitations of single-material systems (InAs has a narrow intrinsic absorption bandwidth, and pure Ti suffers from insufficient radiation stability). Second, a novel triple-resonance mechanism is developed to realize multi-scale light manipulation: Mie resonance at the pyramid apex enables high-efficiency absorption of ultraviolet-near-infrared (UV-NIR) light, Fabry-Perot cavities in the gaps trap mid-infrared light, and plasmonic-semiconductor coupling at the Ti/InAs interface achieves a 3–5-fold enhancement of the local electric field. Third, the symmetric structure ensures polarization independence and incident angle insensitivity, addressing the issue of performance degradation of traditional absorbers under oblique incidence. Finite Difference Time Domain (FDTD) simulations combined with preliminary experimental verification confirm the excellent performance of this design: the broadband average absorption rate in the 280–3000 nm range reaches 99.06 %, and the weighted average absorption efficiency under AM1.5 conditions is 99.02 % with a solar energy loss of only 0.98. It maintains high radiation efficiency at high temperatures: 97.15 % at 1000 K and 97.77 % at 1200 K (benefiting from the high-temperature stability of Ti (melting point: 1668 °C) and the enhanced high-temperature carrier excitation of InAs). Even when the incident angle increases from 0° to 60°, the weighted average absorption efficiency of transverse electric (TE) waves and transverse magnetic (TM) waves remains >91.05 %, outperforming similar symmetric structure. This study realizes the integration of ultra-broadband absorption, high-temperature stable emission, and angle/polarization insensitivity, providing a new paradigm for high-performance solar energy collection and photothermal conversion systems.