A nanocomposite film containing polyoxometalates (POMs) cluster K6P2W18O62 center dot 14H(2)O (P2W18), carbon nanotubes (CNTs) and chitosan (CS) was fabricated by layer-by-layer (LbL) methods. The composite material displays enhanced electrochromic performance, with the optical contrast of 20.3% and coloration efficiency of 91.5 cm(2) C-1 at 620 nm. Furthermore, the composite material displays the increased thickness and surface roughness by incorporation of CNTs into the P2W18 film. Obviously, the presence of CNTs has the strong influence on the multilayer structure, leading to high optical contrast and coloration efficiency. The results demonstrate the essential role of CNTs in enhancing functionality on POMs for applications of electrochromic devices. (C) 2011 Elsevier Ltd. All rights reserved.