A soluble charge-transfer complex is synthesized starting from 7,7',8,8'-tetracyanoquinodimethane (TCNQ) and 2,5-dimercapto1,3,4-thiadiazole dipotassium salt, and characterized by means of spectrophotometric measurements. The material, deposited from the solution phase on the top of doped polythiophene electrodes, provides an elect rochemically reactive charge transport layer, achieving simple design all-organic electrochemical cells to be developed. The devices are characterized by rectification ratios up to 100 at a bias voltage of 3 V, and demonstrate humidity sensor functionality, as indicated by the ratio between the current in the 70% humidity condition and in the dry condition, which is found to reach values of the order of 10(5) at a bias voltage of 3 V. (c) 2007 Elsevier Ltd. All rights reserved.