A nonlinear Fano interaction has been reported here which is manifest in terms of a parabolic temperature-dependent phonon decay process observable in terms of a Raman spectral parameter. Temperature-dependent Raman spectroscopic studies have been carried out on heavily and moderately doped crystalline silicon to investigate the behavior of anharmonic phonon decay in semiconductor systems where Fano interactions are present inherently. Systematic study reveals that in heavily doped systems an interferon-mediated decay route exists for cold phonons present at lower temperatures (<475 K) where Fano coupling is stronger and dominates over the typical multiple-phonon decay process. On the other hand, the anharmonic phonon decay remains the predominant process at higher temperatures irrespective of the doping level. Temperature-dependent phonon self-energy has been calculated using experimentally observed Raman line-shape parameters to validate the fact that the nonlinear decay of phonons through interferon mediation is a thermodynamically favorable process at low temperatures.
Excitation wavelength-dependent Raman spectroscopy has been carried out to study electron–phonon interaction (Fano resonance) in multi-layered bulk 2H–MoS2 nano-flakes. The electron–phonon coupling is proposed to be caused due to interaction between energy of an excitonic quasi-electronic continuum and the discrete one phonon, first-order Raman modes of MoS2. It is proposed that an asymmetrically broadened Raman line shape obtained by 633 nm laser excitation is due to electron–phonon interaction whose electronic continuum is provided by the well-known A and B excitons. Typical wavelength-dependent Raman line shape has been observed, which validates and quantifies the Fano interaction present in the samples. The experimentally obtained Raman scattering data show very good agreement with the theoretical Fano–Raman line-shape functions and help in estimating the coupling strength. Values of the electron–phonon interaction parameter obtained, through line-shape fitting, for the two excitation wavelengths have been compared and shown to have generic Fano-type dependence on the excitation wavelength.
solely by the presence of various electronic equipment's and gadgets. [1][2][3][4] However, as everything comes at the expense of something, the world right now is clearly heading toward some serious shortage of very essential commodities. In order to resonate with the current demand of the society, the major issue at hand that needs to be addressed is the energy crisis we are facing right now. Although, a lot of work is currently going in the industrial front, a good understanding about materials and composites is required for not only making energy storage/conversion, but also energy saving. [5][6][7][8][9] Electrochromic Device (ECD) is one such apparatus that can potentially reduce the energy requirement in buildings, air crafts, automobiles etc., in form of temperature regulators. [10] The basic mechanism of ECDs that includes visible optical changes occurring due to application of some amount of bias is basically driven by redox reactions happening at individual electrodes. [11][12][13] Compatible materials are then chosen and used in a sandwiched manner along with a suitable electrolyte to obtain a final ready-to-use device. [14][15][16] Ever since the birth of Electrochromism by Deb [17,18] a lot of progress in terms of basic parameters like switching speeds, contrast ratio, coloration efficiency etc., has been achieved. Transition Metal Oxides (TMOs like WO 3 ), [19] various polymers (Polythiophene etc) [20,21] metal complexes (like Prussian blue, etc.), [22] and metallo-supramolecular polymers [23] are the materials that act as active layer in an ECD. It is important to mention that when these materials are used in isolation, the devices have little practical application. As a consequence, a device needs to be designed appropriately for optimized operation. Choosing more than one layer has helped in not only improving the device performance, but also in getting multiple color switching. This design, like all others, come with certain constraints that limits the versatility of a device leaving a room for improvement in terms of enhancement of para meters. [10,[24][25][26] Newer ways need to be explored so that a versatile device that can operate with low power consumption, multiple wavelengths and comes with a possibility of integrated in the form of flexible device, can be fabricated.Fundamental applications of ECD such as usage in smart windows of buildings, aircrafts etc., require them to switch Search for a versatile flexible all-organic liquid electrolyte-less solid-state electrochromic device continues. In this quest, a polyaniline-Viologen-(PANI-EV)-based electrochromic device has been reported and designed based on the complementary redox behavior and easy processibility. Electrochromic electrodes are first individually characterized before the device fabrication, to check their compatibility. The polyaniline electrode is electrodeposited and characterized using scanning electron microscopy and Raman techniques followed by bias dependent absorbance measurements to understand its color switching c...
Inorganic oxide electrochromic electrodes can be made more robust by adopting suitable deposition techniques. Electrochemically deposited Tungsten Oxide (WO3) film through chronoamperometry has been studied here for application as electrochromic auxiliary electrode. Thoroughly characterized film using electron microscopy, X-ray diffraction and Raman spectroscopy has been used for electrochromic measurements. The electrode shows reversible transparent to blue color switching when biased with a very small bias of 1V. Bias dependent in-situ spectroelectrochemistry measurements have been performed which shows excellent results in terms of reversibility, cyclability, color contrast, appreciable switching time and good current stability at low working potential. The results thus pave the way to an excellent deposition technique designed particularly for electrochromic applications.
Methods to improve the performance of solid state electrochromic devices (ECDs) need to be explored and the dynamic doping process must be optimized to achieve ideal device performance. Molybdenum disulphide (MoS2) doped ECD has been fabricated by using two conducting polymeric films, i.e. polythiophene (P3HT) and ethyl viologen (EV), to investigate the role of 2D material doping on the overall device performance. Hydrothermally grown MoS2 nanoflowers, characterized using x-ray diffraction, electron microscopy and Raman spectroscopy were used for this purpose. Furthermore, the effect of MoS2 dopant concentration on the performance of an EV/P3HT-based ECD was studied systematically. The prepared solid-state ECD shows improved electrochromic performance in terms of switching speed, color contrast and coloration efficiency while switching its color from one state to the other (magenta and blue) under a very small external bias (±1.4 V). The transition from colored to bleached state is fastest for the highest (0.3 wt%) MoS2-doped ECD, whereas the color contrast and coloration efficiency is maximum for the lowest (0.1 wt%) MoS2-doped device. The variation in electrochromic parameters as a function of dopant (MoS2) concentration reveals that an appropriate concentration must be chosen depending on the requirement
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