E-Paper Displays

11Phase Change Material Displays

Ben Broughton and Peiman Hosseini

11.1 Introduction

Phase change material (PCM) displays are an emerging display technology that can provide highly colored, high reflectivity, fast switching, fully bistable reflective displays, via a mechanism entirely new to display technology – reversible crystallization of optically absorbing, amorphous, ultra‐thin films.

This mechanism, and the PCMs which enable it have been well developed for optical disk and computer memory applications, but until relatively recently had not been explored for their reflective display potential, despite the extremely fast switching and high refractive index change they exhibit. This was likely due to the microscopic areas switched in these devices and their limited optical contrast shown under broadband illumination. Interest in the use of PCMs in white‐light reflective optical devices was initiated by the publication of Hosseini et al. [1], which demonstrated both macroscopic and nanoscopic thermal switching of PCMs incorporated into an ultra‐thin film “strong interference” optical stack, for the first time translating the large change in complex refractive index into a striking change in reflected color. The remainder of this introduction will discuss in more detail the PCMs and switching mechanism, and the optical effect, which were combined in this development.

11.2 Phase Change Materials and Devices

Chalcogenide‐based PCMs are a special class of functional materials ...