Resonant Thermoelectric Nanophotonics

Photodetectors are typically based either on photocurrent generation from electron–hole pairs in semiconductor structures or on bolometry for wavelengths that are below bandgap absorption. In both cases, resonant plasmonic and nanophotonic structures have been successfully used to enhance performance. Here, we show subwavelength thermoelectric nanostructures designed for resonant spectrally selective absorption, which creates large localized temperature gradients even with unfocused, spatially uniform illumination to generate a thermoelectric voltage. We show that such structures are tunable and are capable of wavelength-specific detection, with an input power responsivity of up to 38 V W^(–1), referenced to incident illumination, and bandwidth of nearly 3 kHz. This is obtained by combining resonant absorption and thermoelectric junctions within a single suspended membrane nanostructure, yielding a bandgap-independent photodetection mechanism. We report results for both bismuth telluride/antimony telluride and chromel/alumel structures as examples of a potentially broader class of resonant nanophotonic thermoelectric materials for optoelectronic applications such as non-bandgap-limited hyperspectral and broadband photodetectors

Thermoelectric properties of Ni0.05Mo3Sb5.4Te1.6 composites with NiSb nanocoating

NiSb nanoparticles by 0.034, 0.074 and 0.16 volume fractions were successfully coated on bulk polycrystalline Ni0.05Mo3Sb5.4Te1.6 thermoelectric (TE) particles through a solvothermal route without deteriorating the bulk Ni0.05Mo3Sb5.4Te1.6 material. The samples were consolidated through hot pressing and their thermoelectric (TE) properties were characterized. At 400 K, 500 K, and 600 K, 0.074 NiSb sample exhibited 22%, 16% and 11.3% increases in the power factor (P.F.) compared to bulk material. The main contributing factor to this enhanced power factor is the elevated electrical conductivity. For the same sample, the reciprocal relationship between Seebeck coefficient and electrical conductivity is decoupled. Sample 0.16 NiSb exhibited the highest electrical conductivity among the three samples. The thermal conductivity of the 0.16 sample was less temperature sensitive compared to other samples. HRTEM and SEM tools were applied to comprehend microstructural features and their relationship to TE transport properties. Pore effect on the thermal and electrical conductivity was elucidated. This study shows that grain-boundary manipulation via this wet chemistry technique is indeed an economically viable method to fabricate and optimize the transport properties of bulk TE materials