Electrochromic Inorganic Nanostructures with High Chromaticity and Superior Brightness.

Marika Gugole,Stefano Rossi,Andreas Dahlin,Magnus P Jonsson,Oliver Olsson

doi:10.1021/acs.nanolett.1c00904

Marika Gugole, Stefano Rossi + Show 3 more

Open Access

https://doi.org/10.1021/acs.nanolett.1c00904

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Abstract

The possibility of actively controlling structural colors has recently attracted a lot of attention, in particular for new types of reflective displays (electronic paper). However, it has proven challenging to achieve good image quality in such devices, mainly because many subpixels are necessary and the semitransparent counter electrodes lower the total reflectance. Here we present an inorganic electrochromic nanostructure based on tungsten trioxide, gold, and a thin platinum mirror. The platinum reflector provides a wide color range and makes it possible to “reverse” the device design so that electrolyte and counter electrode can be placed behind the nanostructures with respect to the viewer. Importantly, this makes it possible to maintain high reflectance regardless of how the electrochemical cell is constructed. We show that our nanostructures clearly outperform the latest commercial color e-reader in terms of both color range and brightness.

Highlights

Supported by major advances in nanofabrication techniques, there has been a renewed interest in structural colors based on solid state materials with nanoscale features
Several fully inorganic nanostructures based on metals and tungsten trioxidechhraovme ibceednevpicreesse.8n−t1e4d as In strong candidates for contrast to organic durable electrochromism based on conducting polymers,[15] the use of WO3 does not cause swelling of the material, i.e., the optical tunability is solely a result of the change in permittivity of the material upon ion intercalation.[16]
Inspired by recent work on tunable cavity resonances based on Li+ intercalation in WO3,9−12,21 we evaluated different nanostructures where WO3 was sandwiched between a mirror and a semitransparent metal film with nanoholes, generating a Fabry−Peŕ ot cavity.[11,13,21−23] Colloidal lithography and standard thin film deposition techniques were used, which enable easy production of large-area samples

Summary

■ INTRODUCTION

Supported by major advances in nanofabrication techniques, there has been a renewed interest in structural colors based on solid state materials with nanoscale features. Maintaining high brightness is critical for electronic paper technologies since only a fraction of the display surface will show a given color when using subpixels arranged side by side.[5] Because of this intensity loss, it is essential to find electrochromic surfaces that can provide many different colors as it can reduce the number of subpixels needed. In some cases, this can be achieved with polarization-dependent reflection of colors and liquid crystals,[17] but such approaches still result in low absolute. We propose a dual multichromatic pixel layout (instead of the conventional RGB) that enables high image quality in a reflective color display and show that this clearly can outperform a state-of-the-art electronic reader in color in terms of both brightness and color quality

■ RESULTS AND DISCUSSION

■ CONCLUSIONS

■ REFERENCES