Dicarbocyanine-based organic humidity sensors

Abstract

The utilization of organic dicarbocyanine dye-conjugated molecules, specifically 1,1′-diethyl-4,4′-dicarbocyanine iodide (DDCI-4), as the sensing film in capacitive-type humidity sensors has been demonstrated. The structural, morphological, and wettability characteristics of the sensing films as well as the performance of the electrode gaps of the devices were analyzed. Aluminum (Al)/DDCI-4/Al capacitive humidity sensors were fabricated using solution-processed spin coating techniques in a planar geometry. In this study, a surface profiler was used to measure the size of electrode gaps, which were 94.87 ± 1.20 µm, 391.00 ± 1.53 µm, 902.00 ± 2.08 µm, and 1906.67 ± 3.33 µm. Compared to those with larger gaps (391 µm, 902 µm, and 1907 µm), the device with the smallest gap measured 45 ± 9.1 fF/%RH with the highest sensitivity. In addition, the hysteresis with response and recovery performances has been studied, revealing the lowest values of 0.31%, 6 s, and 9 s, respectively. It is anticipated that the 1,1′-diethyl-4,4′-dicarbocyanine iodide's electronic, ionic, and dipole polarizations are responsible for the excellent performance of dye-based organic humidity sensors.