A Study on the Contribution of Contact Interface Area on Sensitivity of PEDOT: PSS Films to Jasmine Aroma

This paper presents a study on the contribution of various areas in a sensor such as surface area which  mostly depends on the properties of the sensing material and the metal to sensing film contact area which depends on the type of contact being formed, either ohmic or rectifying depending on the work function of the sensing material. In general, the surface area of a sensor has a direct impact on its sensitivity. Sensitivity increases as surface area increases.However, in the case of some sensors, the contact interface area contributes more to sensitivity than the sensor's surface area. Increased contact interface, increases depletion region around the interface, in turn causing larger change for the same input sample. A large interfacial area is beneficial for charge transport. This research work presents an improvement in sensitivity of PEDOT: PSS films when contact interface area between film and copper electrode is increased while keeping sensing surface area to be same. An improvement in sensitivity by about two times is observed when the contact interface is increased by about four times. Operating the sensing films at various flat band regions of the frequency response indicate lower sensitivity of the films at low frequencies(f<5KHZ) due to electric field effect at the contact interface whereas operation at high frequency(3MHz) also results in low sensitivity due to complete by passing of contact interface capacitance. An operating frequency of 10KHz is found to be optimum for maximum sensitivity. Response of the sensor is found to have linear relation with total absorbance spectra of the aroma components analyzed using UV-photospectrometry. The sensor developed is useful for jasmine growing farmers to assess quality of jasmine aroma accurately and fix fair price for the flowers and better economic returns.