Photochromic dyes

Abstract

This article describes the defining characteristics of photochromic dyes and highlights the subset of properties that are of greatest commercial importance. It outlines the history of the industrial exploitation of photochromic colorants before moving on to discuss current and potential applications. In doing so, a brief tour of key types of photochromic dye is provided.

Can we make color switchable photovoltaic windows?

“…While the earliest photochromic systems, utilizing an anthracene-dianthracene photochromic cycle, were described in the 1860s, the rst phenomenon more closely related to modern industrial photochromism was described in 1876 by ter Meer, who described the reversible color change of the potassium salt of dinitroethane from colorless in the dark to red in sunlight. [26][27][28] With early commercial potential identied in the 1950s, by 1969 over 800 photochromic spiropyrans belonging to 46 subclasses had been investigated, yet degradation upon multiple color change cycles remained challenging for commercial applications. 26,27 More recently, stimuli-responsive polymers have been designed which are controlled by an array of stimulants, including temperature, light, pH, and voltage.…”

“…[26][27][28] With early commercial potential identied in the 1950s, by 1969 over 800 photochromic spiropyrans belonging to 46 subclasses had been investigated, yet degradation upon multiple color change cycles remained challenging for commercial applications. 26,27 More recently, stimuli-responsive polymers have been designed which are controlled by an array of stimulants, including temperature, light, pH, and voltage. 29 These responsive polymers are under investigation across a diverse set of applications, but, despite the long and widely varied investigation, most of the commercial value of photochromic dyes is still in their use in eyeglasses which dynamically change their color state, and novelty items.…”

“…29 These responsive polymers are under investigation across a diverse set of applications, but, despite the long and widely varied investigation, most of the commercial value of photochromic dyes is still in their use in eyeglasses which dynamically change their color state, and novelty items. 27 The dye-sensitized solar cell (DSC) architecture, with dye molecules anchored to nanostructured semiconductor thin lms, 30 is of particular note for switchable PV because it can combine the chromism of organic molecules with the electrical output of a DSC. While the basics of such an architecture appear relatively straightforward, it has proven difficult to achieve both PV output and a large change in light transmission.…”

“… 29 These responsive polymers are under investigation across a diverse set of applications, but, despite the long and widely varied investigation, most of the commercial value of photochromic dyes is still in their use in eyeglasses which dynamically change their color state, and novelty items. 27 …”

“… 62 Moreover, the photostability of current commercial photochromic dyes is not sufficient for applications in window glazing. 27 In these two respects, we can learn from past developments in OPV and DSC dye design, but there remain significant hurdles. The optical absorbance of the common DSC electrolytes is a complication, but semi-transparent DSCs have been demonstrated.…”