Roll-to-roll sputtered and patterned Cu2-x O/Cu/Cu2-x O multilayer grid electrode for flexible smart windows.

Hyeong-Jin Seo,Yoon-Chae Nah,Han-Ki Kim

doi:10.1039/c8ra03252a

Abstract

We fabricated cost-effective Cu2−xO/Cu/Cu2−xO multilayer grid electrodes using roll-to-roll (RTR) sputtering and patterning processes for use as transparent and flexible electrodes in flexible smart windows. To optimize the patterned Cu2−xO/Cu/Cu2−xO multilayer grid, the electrical and optical properties of the Cu2−xO/Cu/Cu2−xO multilayer grid electrodes were investigated as a function of grid width and pitch, which directly influence the filling factor of the grid. At the optimized grid width of 16 and pitch of 600 μm, the Cu2−xO/Cu/Cu2−xO multilayer grid had a sheet resistance of 7.17 Ohm per square and an optical transmittance of 87.6%. In addition, the mechanical properties of the optimized Cu2−xO/Cu/Cu2−xO multilayer grid electrode was compared to those of brittle ITO electrodes to demonstrate its outstanding flexibility. To show the potential of the Cu2−xO/Cu/Cu2−xO multilayer grid for smart windows, we fabricated a flexible and transparent thin film heater (TFH) and a flexible electrochromic (EC) device, which are key components of smart windows. The low saturation voltage of the Cu2−xO/Cu/Cu2−xO grid-based TFH and the fast on–off performance of the Cu2−xO/Cu/Cu2−xO grid-based EC device indicates that the RTR-processed Cu2−xO/Cu/Cu2−xO multilayer grid is promising as a low-cost and large-area flexible transparent electrode for high-performance smart windows.

Highlights

IntroductionWe developed a grid-patterned OMO multilayer electrode with a Cu2ÀxO/Cu/Cu2ÀxO structure using a lab-scale roll-to-roll (RTR) sputtering system to replace high-cost ITO electrodes
Multi-functional smart windows equipped with transparent displays, transparent heaters, electrochromic devices, and energy-harvesting devices have attracted signi cant attention as next-generation exterior materials for buildings and automobiles.[1,2,3,4,5] Unlike conventional windows, which pass visible light into the building or automobile, smart windows provide several convenient and smart functions, such as information displays, energy harvesting, self-heating and cleaning, transmittance control, and indoor temperature and light control
In several components of smart windows, exible and transparent thin lm heaters (TFHs) can remove frost or ice by heating the window and exible electrochromic (EC) devices, which can adjust the indoor brightness by controlling the transmittance of the window.[5,6,7]

Summary

Introduction

We developed a grid-patterned OMO multilayer electrode with a Cu2ÀxO/Cu/Cu2ÀxO structure using a lab-scale roll-to-roll (RTR) sputtering system to replace high-cost ITO electrodes. To optimize the grid width and pitch of the Cu2ÀxO/ Cu/Cu2ÀxO multilayer grid, we investigated the electrical and optical properties of the Cu2ÀxO/Cu/Cu2ÀxO multilayer grid as a function of grid width and pitch. The mechanical properties of the Cu2ÀxO/Cu/Cu2ÀxO multilayer as a substitute for a typical sputtered ITO electrode were comprehensively investigated using lab-designed outer and inner bending tests. We used our patterned OMO multilayer grid electrode to fabricate exible TFHs and EC devices to demonstrate their feasibility for application in next-generation exible smart windows

Experimental

Fabrication and evaluation of thin lm heaters and electrochromic devices

Results and discussion

Conclusions