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Öğe Durability and rejuvenation of electrochromic tungsten oxide thin films in LiClO4-propylene carbonate viscous electrolyte: Effect of Ti doping of the film and polyethylene oxide addition to the electrolyte(Elsevier, 2023) Sorar, Idris; Atak, Gamze; Pehlivan, Ilknur Bayrak; Granqvist, Claes G.; Niklasson, Gunnar A.Tungsten oxide and titanium doped tungsten oxide thin films, deposited by sputtering, were immersed in a viscous electrolyte comprised of LiClO4 in propylene carbonate and 2.0 wt% of polyethylene oxide (PEO). Electrochromic properties of the films were investigated by electrochemical techniques and in situ transmittance measurements. Cyclic voltammetry data were taken in the voltage ranges 2.0-4.0 and 1.5-4.0 V vs Li/Li+ for up to 500 cycles. A potentiostatic rejuvenation treatment was then performed on the degraded electrochromic films, at 6.0 V for 20 h, which was subsequently followed by another cyclic voltammetry measurement. Titanium incorporation into tungsten oxide resulted in a small cyclic stability improvement in the 2.0-4.0-V range, whereas less pronounced effects were observed for cycling in the 1.5-4.0-V range. Combining the results of the present study with our previous work, we are able to assess the relative merits of titanium incorporation and PEO addition to the electrolyte for the durability of electrochromic tungsten oxide thin films. Titanium addition was found advantageous for electrochemical durability in the 2.0-4.0-V range, but no clear benefits of PEO in the electrolyte were seen. On the other hand, in the wider 1.5-4.0-V range, tungsten oxide exhibited better durability than titanium-containing films, and this was especially so after rejuvenation in the PEO-containing electrolyte.Öğe Electrochromism of W-In oxide thin films: Implications for cycling durability(Elsevier Science Sa, 2020) Sorar, Idris; Pehlivan, Ilknur Bayrak; Granqvist, Claes G.; Niklasson, Gunnar A.Electrochromic W oxide and W-In oxide thin films were prepared by dual-target reactive DC magnetron sputtering and were cycled voltammetrically in an electrolyte of lithium perchlorate in propylene carbonate. Film degradation was investigated for up to 500 cycles in the voltage ranges 1.5-4.0, 1.7-4.0 and 2.0-4.0 V vs. Li/Li+, and optical transmittance was recorded concurrently. Indium doping was found to be unambiguously detrimental to electrochromic cycling durability, which resolves an outstanding issue related to recently discovered unprecedented durability of potentiostatically pretreated W oxide films backed by In2O3:Sn and gives strong support in favor of beneficial effects of solid-electrolyte interfacial layers.Öğe Electrochromism of W-Ti Oxide Thin Films: Cycling Durability, Potentiostatic Rejuvenation, and Modelling of Electrochemical Degradation(Electrochemical Soc Inc, 2019) Sorar, Idris; Rojas-Gonzalez, Edgar A.; Pehlivan, Ilknur Bayrak; Granqvist, Claes G.; Niklasson, Gunnar A.Thin films of electrochromic W oxide and W-Ti oxide were prepared by reactive DC magnetron sputtering and were cycled voltammetrically in an electrolyte of lithium perchlorate in propylene carbonate. Film degradation was studied for up to 500 voltammetric cycles in voltage ranges between 1.5-4.0 and 2.0-4.0 V vs. Li/Li+. Optically and electrochemically degraded films were subjected to potentiostatic posttreatment at 6.0 V vs. Li/Li+ to achieve ion de-trapping and rejuvenation so that the films partly regained their original properties. Ti incorporation and potentiostatic posttreatment jointly yielded superior electrochromic properties provided the lower limit of the voltage range was above 1.6-1.7 V vs. Li/Li+. Degradation dynamics for as-deposited and rejuvenated thin films was modeled successfully by power-law kinetics; this analysis indicated coexistence of two degradation mechanisms, one based on dispersive chemical kinetics and operating universally and another, of unknown origin, rendered inactive by rejuvenation. The results of the present study are of large interest for the development of electrochromic devices with exceptional durability. (C) 2019 The Electrochemical Society.Öğe Potentiostatic rejuvenation of electrochromic WO3 thin films: Exploring the effect of polyethylene oxide in LiClO4-Propylene carbonate electrolytes(Elsevier, 2020) Sorar, Idris; Pehlivan, Ilknur Bayrak; Bohlin, Jan; Granqvist, Claes G.; Niklasson, Gunnar A.Thin films of electrochromic (EC) W oxide were prepared by reactive DC magnetron sputtering and were immersed in electrolytes of LiClO4 in propylene carbonate with 0.5-3.0 wt% of added polyethylene oxide (PEO). Charge density and optical modulation range were found to diminish monotonically upon prolonged voltammetric cycling with concurrent optical transmittance measurements for up to 500 and 200 cycles in the voltage ranges 2.0-4.0 and 1.5-4.0 V vs. Li/Li+, respectively. Rejuvenation of the degraded EC films was then accomplished by potentiostatic treatment at 6.0 V vs. Li/Li+ for 20 h and has been ascribed to expulsion of trapped Li ions. Importantly, degradation subsequent to rejuvenation was found to progress at a significantly lowered pace than for as-deposited films in proportion with the amount of PEO especially for harsh voltammetric cycling in the voltage range 1.5-4.0 V vs. Li/Li+. The results of this explorative study are of considerable value for the development of highly durable EC devices such as polymer-laminated smart glazing for energy efficient buildings with excellent indoor comfort.
