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"Film elektrokromik mempunyai spektrum transmisi yang dapat berubah secara reversibel apabila diberi tegangan listrik. Perubahan ini mengganti keadaan tidak tembus cahaya (opaque) ke keadaan bening (transparent) atau sebaliknya, sehingga film dapat digunakan untuk mengatur pancaran cahaya. Dalam makalah ini dilaporkan studi tentang film polianilin sebagai salah satu bahan aktif elektrokromik. Dalam keadaan reduksi, warna film kuning transparan dan dalam keadaan oksidasi hijau sampai biru. Divais elektrokromik yang dibuat terdiri atas lapisan kaca konduktif − film polianilin − elektrolit − kaca konduktif dengan melibatkan larutan 1.0M H2SO4. Pengukuran rapat arus menghasilkan voltamogram untuk beberapa kecepatan perubahan tegangan, sedangkan karakteristik optik diukur dengan spektroskopi UV-Vis. Untuk memeriksa sifat pengaturan cahaya, diturunkan harga intensitas pancaran matahari yang melewatinya. Diperoleh bahwa dalam keadaan reduksi, 70% pancaran menembus divais, sedangkan dalam keadaan oksidasi, pancaran tersebut tinggal 11%. Hasil pengujian reversibiltas menunjukkan bahwa umur pakainya di atas 5.000 siklus.

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Study on Electrochromic Effect of Polyaniline Film. The light transmission factor of an electrochromic film changes reversibly with the application of an electrical voltage. Thereby the transparent film becomes reversibly opaque so that it may be used to control light transmission. In this paper the results of a study on polyaniline film as an electrochromic active material is reported. Polyaniline looks yellow transparent in the reduced state and turns to green-blue at its oxidized state. The electrochromic device considered in this paper was fabricated in planar configuration of ITO glass − polyaniline film − electrolyte − ITO glass which involved 1.0M H2SO4 solution. The measurement of the current density yields voltamograms for several values of the rate of voltage change, while the optical characteristics were measured with ultraviolet-visible spectroscopy. To inspect the light control properties, the intensity of solar radiation propagating through the device was derived. It is found that in its reduced state, the device transmits 70% of the incoming radiation, while in the oxidized state only 11% of the radiation is left. The result of recycling test indicated that film is stable over 5,000 cycles."

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ABSTRACTTungsten oxide, has many interesting optical, electrical, structural, and chemicalproperties, are an ideal choice material for electrochromic smart windows devices. Inthis study, tungsten oxide thin films were prepared by the thermal oxidization onTungsten/ITO/glass substrates at different heat-treatment temperatures. The optimumheat-treatment temperature, corresponding to the maximum electrochromicperformance, was achieved by 550 oC. X-ray diffraction (XRD) analysis indicates thata tetragonal WO3 phase formed at temperatures below 550 oC and the phasetransformed to monoclinic W18O49 after the temperature was raised to 650 oC. Theelectrical properties analysis confirmed that the highest electrical conductivity showthe superior electrochromic performance, with the maximum coloration efficiencyvalue of 60.4 cm2/C. The tetragonal WO3 films, with heat-treatment temperature 550oC and 450 oC, exhibit good electrochromic properties such as a high diffusioncoefficient (1.7x10-11 cm2/s), fast electrochromic response time (coloration time 1.6 s,bleaching time 1.2 s), and high coloration efficiency (60.4 cm2/C).Furthermore, tungsten oxide nanowires were prepared on a tungsten film(W)/ITO-glass substrate at 500 oC for electrochromic devices using the heat-treatment technique. The electrical properties analysis confirmed that the highest electricalconductivity achieve the superior electrochromic performance with the maximumcoloration efficiency value. The tungsten oxide nanowires shows excellentelectrochromic properties such as a higher diffusion coefficient (2x10-9 cm2/s), fasterelectrochromic response time (coloration time 1.7 s, bleaching time 1.1 s), and highercoloration efficiency (67.41 cm2/C) than other tungsten oxide films withoutnanowires. Therefore, the tungsten oxides nanowire prepared by heat-treatmenttechnique, corresponding to the maximum electrochromic performance, would befurther adopted in the commercial application of smart windows."

"This research focuses on developing a characterization method to observe changes in the optical properties of metal oxide materials, particularly BiVO4, during real-time electrochemical processes. This spectroelectrochemical method combines absorbance measurements of the material using UV-vis spectroscopy with electrochemical measurements using cyclic voltammetry simultaneously. The study successfully identified changes in the optical properties of BiVO4 within the potential sweep range of -0.4 VRHE to 2.1 VRHE, due to the electrochromic properties of vanadium in BiVO4. Correlation analysis of optical and electrochemical measurements showed that these optical changes result from oxidation and reduction reactions occurring during cyclic voltammetry. Electron injection into BiVO4 reduces V5+ to V4+, and the oxidation reaction proceeds in the reverse direction. This reaction explains the color change of the sample from yellow to black as vanadium is reduced and oxidized. These changes in oxidation state also result in localized electrons in the material during the electrochemical process. The spectroelectrochemical measurements provide significant insights into the processes affecting the optical properties of BiVO4 during electrochemical processes. This fundamental knowledge is essential for making new advancements in enhancing the performance of electrochemical cells to optimize electrochemical reactions for various applications.

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Penelitian ini berfokus untuk membuat metode karakterisasi yang dapat melihat perubahan sifat optik pada material metal oksida, terutama pada BiVO4, ketika sedang menjalani proses elektrokimia secara real time. Metode spektroelektrokimia ini menggabungkan antara pengukuran absorbansi material menggunakan spektroskopi UV-vis dengan pengukuran elektrokimia secara voltametri siklik secara simultan. Studi ini berhasil mendapatkan perubahan sifat optik pada BiVO4 dalam rentang potential sweep -0.4 VRHE hingga 2.1 VRHE akibat dari sifat elektrokromik unsur vanadium pada BiVO4. Hasil analisis korelasi pengukuran optik dan pengukuran elektromia menunjukkan bahwa perubahan sifat optik ini akibat adanya reaksi oksidasi dan reduksi yang terjadi dalam proses voltametri siklik. Injeksi elektron ke BiVO4 mereduksi V5+ menjadi V4+ dan reaksi oksidasi akan berjalan sebaliknya. Reaksi ini menjelaskan perubahan warna sampel dari warna kuning ke hitam saat vanadium tereduksi dan teroksidasi. Perubahan keadaan oksidasi ini juga mengakibatkan adanya elektron yang terlokalisasi pada material saat menjalani proses elektrokimia. Elektron terlokalisasi ini menciptakan adanya elektron polaron yang mengakibatkan adanya keadaan donor sementara di antara pita valensi dan pita konduksi. Studi ini memperlihatkan bagaimana pengaruh dari potensial dan densitas arus terhadap perubahan sifat penyerapan cahaya dari sampel BiVO4. Hasil pengukuran spektroelektrokimia ini memberikan banyak pengetahuan terkait proses yang terjadi pada sifat optik BiVO4 dalam proses elektrokimia. Pengetahuan fundamental ini dibutuhkan untuk membuat langkah baru dalam meningkatkan performa dari sel elektrokimia untuk mengoptimalkan reaksi elektrokimia yang terjadi untuk berbagai macam aplikasi.

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