Hybrid lead halide perovskites have emerged as an important class of optoelectronic materials. A creative choice of "A"-site organic cations produces hybrid perovskites with reduced dimensionality and intriguing light−matter interactions. Nonlinear optical effects are expected to be stronger in one-dimensional (1D) lead halides compared to those in their 2D or 3D analogues due to greater quantum and dielectric confinements. We performed an extensive probe of the third harmonic generation (THG) properties in 1D pyridinium lead iodide single crystals for the first time. An efficient THG with a high laser-induced damage threshold is the highlight of this system. THG is selectively enhanced for excitation at an optical communication wavelength (1.5 μm) corresponding to band gap resonance. A strong exciton−phonon interaction results in highly Stokes-shifted self-trapped excitonic emission in the 5−300 K temperature range. An interplay between anharmonicity and dynamic disorder dictates the emission properties, further complicated by an isostructural phase transition at 170 K.
Two new molecular organic−inorganic hybrid halogenometallates [BnNMe 2 R]CdBr 4 (Bn = benzyl; 1: R = Me; 2: R = n-Pr) have been synthesized and found to crystallize in the acentric crystal systems suitable for ferroelectric behavior. Both these compounds exhibit well-resolved rectangular polarization vs electric field (P−E) hysteresis loops at room temperature for their polycrystalline thin films. Compounds 1 and 2 exhibited fairly high remnant polarization (P r ) values of 18.59 and 14.24 μC cm −2 , respectively. Moreover, flexible composite thin films of these halogenometallate salts with poly-(dimethylsiloxane) (PDMS) were prepared and employed as mechanical energy-harvesting devices using an impact test setup operating at a frequency of 25 Hz and an applied force of 40 N. The maximum output voltages of 52.9 and 63.8 V have been recorded for the PDMS-fabricated devices of 5 wt % of 1 and 10 wt % of 2, respectively. Also, the obtained power densities of 13.8 and 37.1 μW cm −2 for the respective 5 wt % 1−PDMS and 10 wt % 2−PDMS devices are much higher than all known devices made up of organic− inorganic hybrid materials embedded in PDMS. The energy harvested from these devices was further utilized to charge a capacitor through a full wave-bridge rectifier.
Organic−inorganic ABX 3 hybrids with perovskite structures have drawn enormous attention owing to their intriguing chemical variability, structural tunability, and diversity of application-worthy properties. Herein, we report the synthesis of a new neutral ABX 3 hybrid ferroelectric compound [Me 3 NCH 2 CH 2 OH]CdCl 3 (1), which exhibits a 1D chain structure of edge-sharing CdCl 5 O octahedra that are connected to cationic [Me 3 NCH 2 CH 2 OH] + units via its peripheral OH functionality. The single-crystal X-ray diffraction analysis of the compound at 363 K reveals the conversion of 1 to its coordination isomer 1′, in which the anionic chain consists of face-sharing CdCl 6 octahedra and the cations are uncoordinated. The piezoresponsive force microscopy analysis performed on a single crystal of 1 confirms the existence of polarizable domains in it. The ferroelectric P−E loop measurements on 1 show a high remnant polarization value of 17.1 μC cm −2 . Composite devices based on 1 and polydimethylsiloxane (PDMS) prepared with varying wt % compositions are examined for mechanical energy harvesting applications. The highest open-circuit voltage of 55.2 V and a maximum power density of 70.9 μW cm −2 at an optimal load of 4 MΩ were obtained for the 15 wt % 1−PDMS device. The harvested energy is shown to be effective for capacitor charging and light-emitting diode (LED) flash lighting applications.
A triboelectric
nanogenerator (TENG) based on natural seeds and
electrospun poly(vinyl difluoride) (PVDF) fibers is reported. The
nanofibers are specifically used to enhance the triboelectric effects.
A mustard (flax) seed based TENG renders an impressively high electrical
output with an average open circuit voltage of 84 V (126 V) and maximum
power density 334 mW m–2 (324 mW m–2) under an impact force of 40 N at 25 Hz. Basil seeds are relatively
weaker in power delivery. By comparing the seed crust properties and
TENG performances, we analyze the powering capability in terms of
the cellulose content in the crust, dielectric constant, and surface
morphological features.
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