Wide range highly sensitive relative humidity sensor based on series combination of MoS2 and PEDOT:PSS sensors array

Abstract

In this work, a polymeric material poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and a two dimensional material molybdenum disulfide (MoS2) 2D nanoflakes have been employed as the active layers of two separate transducers on a single substrate for the detection of relative humidity. The portion with MoS2 based active region showed high responsivity towards low humidity levels while PEDOT:PSS based portion responded well to high humidity levels. These two sensing portions were connected in a series combination to fabricate a single humidity sensing device capable to respond to a wide range of relative humidity with very high sensitivity. 2D MoS2 nanoflakes were obtained by aqueous exfoliation of pristine MoS2. The transducer electrode pairs were fabricated using reverse offset printing technique on a piezoelectric LiNbO3 substrate. The active thin film of MoS2 flakes was deposited by Electrohydrodynamic atomization (EHDA) while the thin film of PEDOT:PSS was deposited by SAW-EHDA hybrid system. The fabricated sensor is capable of sensing relative humidity with high sensitivity (50 kΩ/%RH or 800 Hz/%RH) in a wide range of 0%RH–80%RH. The response and recovery times are also excellent with values of 0.5 s and 0.8 s respectively. This unique approach of combining multiple transducers in a single sensing device can lead to the development of high performance sensors and can solve the current limitations of single transducer based sensing devices.