Large-area flexible monolithic ITO/WO3/Nb2O5/NiVOχ/ITO electrochromic devices prepared by using magnetron sputter deposition

• An all-solid-state inorganic large flexible ECD was successfully prepared by reactive-magnetron-sputtering.
• The optical transmittance for bleached and colored states can ultimately be 53% and 11% at applied voltage of ±3 V, respectively.
• The bending radius of curvature was larger than 7.5 cm. The response time is less 6 s for coloring and 5 s for bleaching.
• The ECD can tolerate the bending at a critical radius of curvature of 7.5 cm and sustaining over 8,000 cycles of coloring and bleaching.

Electrochromic devices (ECDs) have been applied in smart windows to control the transmission of sunlight in green buildings, saving up to 40–50% electricity consumption and ultimately reducing carbon dioxide emissions. However, the high manufacturing costs and difficulty of transportation of conventional massive large area ECDs has limited widespread applications. A unique design replacing the glass substrate commonly used in the ECD windows with inexpensive, light-weight and flexible polymeric substrate materials would accelerate EC adoption allowing them to be supplemented for regular windows without altering window construction. In this study, an ITO/WO3/Nb2O5/NiVOχ/ITO all-solid-state monolithic ECD with an effective area of 24 cm × 18 cm is successfully integrated on a PET substrate by using magnetron sputter deposition. The electrochromic performance and bending durability of the resultant material are also investigated. The experimental results indicate that the ultimate response times for the prepared ECD is 6 s for coloring at an applied voltage of −3 V and 5 s for bleaching at an applied voltage of +3 V, respectively. The optical transmittances for the bleached and colored state at a wavelength of 633 nm are 53% and 11%, respectively. The prepared ECD can sustain over 8000 repeated coloring and bleaching cycles, as well as tolerate a bending radius of curvature of 7.5 cm.