Quantification of the short-range order in amorphous silicon has been formulized using Raman scattering by taking into account established frameworks for studying the spectral line-shape and size dependent Raman peak shift. A theoretical line-shape function has been proposed for representing the observed Raman scattering spectrum from amorphous-Si-based on modified phonon confinement model framework. While analyzing modified phonon confinement model, the term "confinement size" used in the context of nanocrystalline Si was found analogous to the short-range order distance in a-Si thus enabling one to quantify the same using Raman scattering. Additionally, an empirical formula has been proposed using bond polarizability model for estimating the short-range order making one capable to quantify the distance of short-range order by looking at the Raman peak position alone. Both the proposals have been validated using three different data sets reported by three different research groups from a-Si samples prepared by three different methods making the analysis universal.

An "all-inorganic", fast, and power-efficient solid-state electrochromic device has been realized by choosing Co 3 O 4 and PB films as complementing electrodes. The prussian blue and cobalt oxide films have been synthesized via a simple galvanostatic method to achieve better film quality to be used in a device. Prior to fabricating a prototype solid-state device, the electrodes have been tested using in situ electrochemical and spectroscopic studies. This is followed by fabricating a solid-state device that shows switching between multiple colors with an applied bias of less than a couple of volts. A moderate color contrast of ∼40% with 1.5 s switching time has been observed with showing stability for more than 900 s of continuous switching. A redoxdriven electrochromic behavior of individual electrodes makes it possible for the solidstate device to show beautiful colors with a small applied bias. Electrochemical and spectroscopic measurements have been carried out to establish the possible mechanism of color switching shown by the device. Moreover, a coloration efficiency of ∼250 cm 2 /C makes it comparable to an "all-organic" or hybrid solid-state device, with its strong nature being an additional advantage.

A fast and flexible all-organic electrochromic device, fabricated using polythiophene and PCBM as active materials and plastic substrate, which shows very good power efficiency as well, has been reported here. The device shows quantifiable improvement in electrochromic performance using parameters like switching speed, coloration efficiency, color contrast, and cycle life. Spectroscopic investigations have been carried out using Raman and UV–vis to establish a bias induced redox switching based mechanism for the reported improvement in the performance. The device shows switching between magenta (OFF) and transparent states (ON) with a very small bias of ±1 V, an optical modulation of 50% and an absorbance switching contrast of 91%. An enhanced stability for a duration of longer than 2500 s and 250 cycles has been reported with an ultrafast response of few hundred milliseconds. A very high coloration efficiency of 321 cm2/C is achieved, making the proposed device one of the best reported P3HT-based electrochromic devices.

Pictorial representation of the as-prepared device in ON and OFF states with its in situ absorbance spectra at various applied biases.

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