Lead halide perovskites have exhibited excellent performance in solar cells, LEDs and detectors. Thermal properties of perovskites, such as heat capacity and thermal conductivity, have rarely been studied and corresponding devices have barely been explored. Considering the high absorption coefficient (10 4 ~10 5 cm −1 ), low specific heat capacity (296–326 J kg −1 K −1 ) and small thermal diffusion coefficient (0.145 mm 2 s −1 ), herein we showcase the successful use of perovskite in optoacoustic transducers. The theoretically calculated phonon spectrum shows that the overlap of optical phonons and acoustic phonons leads to the up-conversion of acoustic phonons, and thus results in experimentally measured low thermal diffusion coefficient. The assembled device of PDMS/MAPbI 3 /PDMS simultaneously achieves broad bandwidths (−6 dB bandwidth: 40.8 MHz; central frequency: 29.2 MHz), and high conversion efficiency (2.97 × 10 −2 ), while all these parameters are the record values for optoacoustic transducers. We also fabricate miniatured devices by assembling perovskite film onto fibers, and clearly resolve the fine structure of fisheyes, which demonstrates the strong competitiveness of perovskite based optoacoustic transducers for ultrasound imaging.
Metal nanoparticles hold promising applications in photoacoustic transducers due to their unique plasmonic properties. However, current transducers using conventional noble metal nanoparticles exhibit relatively low photoacoustic conversion efficiency, primarily due to insufficient optical absorption for effective thermal or acoustic energy conversion. This paper proposes the use of nanoparticles derived from the liquid metal gallium-indium eutectic alloy (EGaIn), which demonstrate significantly higher absorption at 1064 nm compared to gold or silver nanoparticles, thereby enhancing photoacoustic conversion efficiency. To stabilize the liquid metal nanoparticles (LMNPs) in a polydimethylsiloxane (PDMS) matrix, 3-mercaptopropyltriethoxysilane (MPTMS) is employed as a surfactant during sonication in a solvent. Furthermore, embedding EGaIn nanoparticles in a cluster form enhances absorption through gap-induced plasmonic effects. Through optimization, a photoacoustic conversion efficiency of 5.1 × 10−3 is achieved, which is 1–2 orders of magnitude higher than those of transducers using conventional metal materials. This study highlights the potential of liquid metal nanoparticles with plasmonic effects in advancing the development of novel photoacoustic composite materials.
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