A complementary electrochromic device (ECD) based on Prussian blue (PB) and poly(3,3-diethyl-3,4-dihydro-2H-thieno-[3,4-b][1,4]dioxepine) (PProDOT-Et-2) has been systematically investigated. PB is regarded as an anodic coloring material with high electrochemical stability, while PProDOT-Et-2 is a cathodic coloring polymer with high contrast and high coloration efficiency (eta). The electro-optical properties of the two electrochromic (EC) materials are characterized separately in a 0.1 M LiClO4 in propylene carbonate (PC). A complementary ECD is assembled based on the two EC materials. The maximum transmittance of the ECD at 590 nm can be changed reversibly from 11.3% to 70.6% at the applied voltages of 1.2 and -1.3 V. and achieved a high coloration efficiency of 1214 cm(2)/C. Moreover, this ECD still remains at 98% of its maximum transmittance window (Delta T-max) even after 1,200 cycles, namely, the Delta T value decreases from 59% to 58%. (C) 2011 Elsevier B.V. All rights reserved.