Planar capacitive type humidity sensor fabricated using PTB7-Th by facile solution processing approach

A capacitive humidity sensor using coplanar electrodes coated with poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-) -2-carboxylate-2-6-diyl](PTB7-Th) thin film (Al/PTB7-Th/Al) has been fabricated and investigated. In the present work, we show that increased sensitivity is obtained by rough and non-uniform surface morphology of the polymer thin film which comprises distinct peaks and valleys. The sensor shows good sensing behavior with enhanced sensitivity, better linearity and larger bandwidth. The device showed sensitivity over an appreciable range of relative humidity levels (between 20 and 95% RH). Typical adsorption and desorption response times were measured to be 20 s each.