Electrochromic Glass vs. PDLC – Smart Glass Technology Comparison

December 11, 2013
Smart glass is intended to have the ability to control the amount of light, and heat, passing through. With a switch of a button on a wall or smart phone app, the glass can change from transparent to completely opaque. Unlike blinds, smart windows are capable of partially blocking light while maintaining a clear view of what lies behind the window.

Smart glass technologies include electrochromic, photochromic, suspended particle, and liquid crystal device technologies.

While the basic concept behind all smart windows is the same, they can be made in several different ways, each with a different method and properties for blocking light. Critical aspects of smart glass include material costs, installation costs, electricity costs and durability, as well as functional features such as the speed of control, possibilities for dimming, and the degree of transparency.

Electrochromic Glass & Film
Electrochromic requires new glass installation (no film option to apply on existing glass. Windows consist of two glass panes with several layers sandwiched in between. It works by passing low-voltage electrical charges across a microscopically-thin coating on the glass surface, activating an electrochromic layer which changes color from clear to dark. The electric current can be activated manually or by sensors which react to light intensity. One advantage of the electrochromic smart window is that it only requires electricity to change its opacity, but not to maintain a particular shade.

In electrochromic windows, the electrochromic material changes its opacity: it changes between a colored, translucent state (usually blue) and a transparent state. A burst of electricity is required for changing its opacity, but once the change has been effected, no electricity is needed for maintaining the particular shade which has been reached. Darkening occurs from the edges, moving inward, and is a slow process, ranging from many seconds to several minutes depending on window size.

The switching speed of electrochromic glass is slowest overall and varies depending upon the size of the panel (larger panels typically take many minutes to switch). The consistency of tint changes also varies, with larger panels sometimes exhibiting tint changes that begin at the glazing’s outer edges and then move inward (known as the “iris effect”).

The switching speed of electrochromic glass is slowest overall and varies depending upon the size of the panel (larger panels typically take many minutes to switch). The consistency of tint changes also varies, with larger panels sometimes exhibiting tint changes that begin at the glazing’s outer edges and then move inward (known as the “iris effect”).

Polymer Dispersed Liquid Crystal Technology
PDLC stands for polymer dispersed liquid crystal. Liquid crystals are well known for flat panel displays. Liquid crystal display, LCD is the most popular flat panel displays which are applied in daily use products such as portable computer, cellular phones, calculators, digital clocks and watches, etc. In LCD, electricity is used to change the shape of liquid crystals to allow light to pass through and thus forming colors, images, figures and numbers on the displays.

In polymer dispersed liquid crystal, it is just simply a combined application of polymers and liquid crystals. Liquid crystals respond to an electrical charge. When current flows, each crystal droplet is activated to align parallel permitting light passes through resulting in transparency. When electrical charge is absent, liquid crystals droplets are randomly oriented. Light is heavily scattered. It does not permeate in a straight way and thus, resulting in opaque.

Smart Glass Technology
PDLC Technology Vs. Electrochromic Technology Recap
PDLC Technology

Can be used for interior and exterior glass applications
Switches from clear to opaque in less than a second
Runs on standard 110 v
Available in a self-adhesive switchable film that can be applied to existing windows and laminated smart glass
Provides total privacy in its opaque state (cannot see through it)
Electrochromic Technology

Used for exterior glass applications only
Long transition to switches from clear to opaque. Larger windows can take 5-10 minutes
New glass must be installed. No film option for existing glass
Not used for privacy (you can still see through it in its opaque state)