Nanocrystalline porous CdSe thin films with particle diameter of 6.0 and 8.0 nm were prepared by chemical deposition on SnO2 conducting glass substrates. The broadening of the excitonic transitions in the absorption spectrum due to the size distribution and an increase of bandgap energy compared with the bulk CdSe are observed. Electrolyte electroabsorption (EEA) spectrum measured in polysulfide solution exhibits the characteristic second derivative lineshape of the quantum-confined CdSe nanoparticles. A quadratic modulation voltage dependence of EEA signals indicates that the electrical field distribution of nanocrystalline porous CdSe thin films is different significantly from that of bulk CdSe thin films. (c) 2004 Elsevier B.V. All rights reserved.