Solution‐Processed Lead Iodide for Ultrafast All‐Optical Switching of Terahertz Photonic Devices

Abstract

technological relevance, currently there is a huge quest for ultrafast switchable/tunable metasurfaces that possess low threshold switching and easy fabrication techniques. Recent progress and new approaches on tunable metasurfaces [12] based on spincoating and thermal evaporation [13] of semiconductors on metasurfaces have given promising pathways for realizing ultrasensitive, low energy ultrafast devices. Among them solution-processed organic-inorganic perovskites have shown promising pathways in realizing tunable metasurfaces with their easy fabrication techniques and excellent photoresponsive properties. [14][15][16] Further, solution processed perovskites have shown to exhibit plasmonic behavior and have emerged as novel platform for realizing tunable metasurfaces at optical frequencies. [17,18] In the recent studies, it was shown that by photodoping the solution-processed methyl ammonium lead iodide (CH 3 NH 3 PbI 3 ) perovskite materials spin coated on the metasurface aids in ultrasensitive reconfiguration of its resonances on rigid and flexible substrates at THz frequencies. [19,20] However, the switching speed in these hybrid devices is limited to nanoseconds that is dictated by the recombination lifetimes of the photoexcited free carriers in the perovskite thin films.The other class of solution processed compounds such as metal-halides show promising features to enhance the optoelectronic properties of perovskites by modifying their absorbance and photocarrier lifetimes. Such compounds with more simpler preparation techniques would provide an ideal platform for photoswitching applications on rigid as well as flexible photonics platforms. Among the metal-halides, the solutionprocessed lead iodide (PbI 2 ) precursor was found to play a significant role than envisaged in dictating the performance and quality of the perovskite-based photovoltaic devices. Concerned with its toxicity, many attempts are being carried out to replace the lead-based legends in perovskites, nevertheless, the rich chemical and photophysical properties of lead-iodide in enhancing the photovoltaic [21] and light-emitting properties [14] of hybrid perovskites has been phenomenal compared to other metal-halide compounds. Recent studies have shown that the remnant PbI 2 on the perovskite films passivate the defects in the grain boundaries thereby enhancing the photoconversion efficiency (PCE) of the lead-iodide-based hybrid perovskite solar cells. [22][23][24] Varying the initial mole fractions of PbI 2 in Solution-processed lead iodide (PbI 2 ) governs the charge transport characteristics in the hybrid metal halide perovskites. Besides being a precursor in enhancing the performance of perovskite solar cells, PbI 2 alone offers remarkable optical and ultrasensitive photoresponsive properties that remain largely unexplored. Here, the photophysics and the ultrafast carrier dynamics of the solution processed PbI 2 thin film is probed experimentally. A PbI 2 integrated metamaterial photonic device with switchable picosecond time response at...

Ultrafast Frequency Shift of Electromagnetically Induced Transparency in Terahertz Metaphotonic Devices

“…During the past decade, the THz metaphotonics devices comprising the active media and meta-atoms have been widely applied in modulators, which has greatly changed conventional approaches of THz wave manipulation. [17][18][19][20][21][22][23] Precisely, the meta-atom resonated with THz incident waves is a composite artificial "atom" that can offer extraordinary DOI: 10.1002/lpor.201900338 ability of strong light-matter interactions unattainable in natural materials. [24,25] Importantly, the exotic electromagnetic response is determined by the resonator structures.…”

“…These practical THz applications naturally stimulate further research on the efficient THz emission, modulation and detection. During the past decade, the THz metaphotonics devices comprising the active media and meta‐atoms have been widely applied in modulators, which has greatly changed conventional approaches of THz wave manipulation . Precisely, the meta‐atom resonated with THz incident waves is a composite artificial “atom” that can offer extraordinary ability of strong light‐matter interactions unattainable in natural materials .…”

Programmable Single‐Crystalline PbI2 Microplate Arrays and Their Organic/Inorganic Heterojunctions

“…Here, lead (II) iodide (PbI 2 ) is selected because of its solution processability and wide applications in photovoltaics, lasers and photodetectors. [31][32][33][34][35] We successfully prepared PbI 2 single-crystalline arrays with the smooth surface, controllable morphology and ordered crystallographic orientation. Through designing the pattern of micropillars, we also achieved a series of programmable patterns of single-crystalline PbI 2 microplate arrays, including 26 Latin characters (A-Z), Arabic numeral characters (0-9) and mathematical symbols.…”

Reconfigurable metamaterials for optoelectronic applications

“…[15] In 2020, Lin et al designed a three-dimensional structured graphene metamaterial to achieve omnidirectional solar thermal energy conversion. [16] There are also many corresponding reconfigurable metamaterial breakthroughs [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] in this decade apart from these relatively milestone research developments.…”