Accelerated durability testing of electrochromic windows

Prototype electrochromic windows made by several different US companies hav e been tested in our laboratory for their long-term durability. Samples wer e subjected to alternate coloring and bleaching voltage cycles while expose d to simulated 1-sun irradiance in a temperature-controlled environmental c hamber with low relative humidity. The samples inside the chamber were test ed under a matrix of different conditions. These conditions include: cyclin g at different temperatures (65, 85 and 107 degrees C) under the irradiance , cycling versus no-cycling under the same irradiance and temperature, test ing with different voltage waveforms and duty cycles with the same irradian ce and temperature, cycling under various filtered irradiance intensities, and simple thermal exposure with no irradiance or cycling. The electro-opti cal characteristics of the samples were measured between 350 and 1,100 nm e very 4,000 cycles for up to 20,000 cycles. Photographs of the samples were taken periodically with a digital camera to record cosmetic defects, the ex tent of residual coloration, and overall coloration and bleaching uniformit y of the samples. Our results indicate that the most important cause of deg radation is the combination of continuous cycling, elevated temperature and irradiance. The relative importance of these variables, when considered sy nergistically or separately, depends on the particular device materials and design. (C) 1999 Elsevier Science Ltd. All rights reserved.