Sensors and Actuators A 299 (2019) 111574 Contents lists available at ScienceDirect Sensors and Actuators A: Physical journal homepage: www.elsevier.com/locate/sna Fabrication of P-N heterojunction based MoS 2 modified CuPc nanoflowers for humidity sensing Abir Jana a,∗ , Komal Kumari a , Anup Dey a , P.S. Sreenivas Reddy b , Bikram Biswas a , Bhaskar Gupta a , Subir Kumar Sarkar a a Department of E.T.C.E, Jadavpur University, Kolkata, West Bengal, 700032, India b Nalla Narasimha Reddy Educational Society’s Group of Institutions, Korremula X Road, Via Narapally, Ghatkesar Mandal, Chowdariguda, Telangana, 500088, India a r t i c l e i n f o Article history: Received 5 July 2019 Received in revised form 19 August 2019 Accepted 24 August 2019 Available online 12 September 2019 Keywords: CuPc nanoflowers Humidity sensing Organic-inorganic p-n heterojunction Device aging a b s t r a c t In recent times, there has been an increased demand for cost-effective, robust and highly reliable humid- ity sensors. 2D material MoS 2 (n-type) have demonstrated their potential application in chemical and humidity sensing. In this work, an organic-inorganic p-n heterojunction based sensor has been fabri- cated using the inorganic MoS 2 and the organic CuPc, and its viability towards humidity sensing has been experimentally demonstrated. The thin film sensor was characterized by SEM and the results revealed the formation of CuPc nanoflowers on MoS 2 surface. The XRD results also indicate excellent crystalliza- tion. The sensor shows reduced resistance with increasing RH% and the variation has been observed to be almost linear. The sensing range is from 20% RH to 98% RH. The measured sensitivity is 0.615 M/%RH. The demonstrated results are of great interest in terms of sensitivity, linear response, range of humidity monitoring and stability. © 2019 Elsevier B.V. All rights reserved. 1. Introduction Recent advancements in the field of sensor technologies have resulted in low-power, miniaturized, high speed and cost effective sensors. Humidity is a crucial ambient parameter which needs to be monitored for a wide range of applications such as automated systems, instrumentation, climatology, agriculture, etc. Ceramic, semiconductor and organic polymer based materials have been utilized for fabrication of humidity sensors [1–9]. The sensing mate- rials suitable for high performance humidity sensors must have-(a) high surface to volume ratio for better physisorption of water molecules, (b) the ability to interact with the water molecules repeatedly for enhanced life-cycle and faster response times. When Humidity may be given in terms of’ Relative Humidity’, ‘Parts Per Million’ by weight or by volume and ‘Absolute Humidity’. Most humidity sensors are calibrated to measure Relative humidity. Relative humidity in percentage is expressed as follows: RH = (H A /H S )×100 ∗ Corresponding author. E-mail address: abirjana.etce.rs@jadavpuruniversity.in (A. Jana). where, H A =Absolute Humidity; H S =Saturation Humidity Nano- materials including nanowires, nanorods, nanofibers and pn- heterojunctions have been explored widely as sensing materials owing to high surface to volume ratios that is inherent in them [10,11]. These hygrometric sensors utilize the variation in their electrical and physical properties in the presence of atmospheric humidity to provide a measure of this humidity, based on adsorp- tion or desorption of water molecules. Ceramic materials offer superior advantages over other existing humidity sensing mate- rials. The porous nature of ceramics (inorganic) plays a vital role in physisorption of water molecules making them suitable for humid- ity sensing. Intergranular and intragranular as well as pore size distribution determine the performance of these sensing materi- als. These inorganic sensing materials also offer the advantages of mechanical strength, thermal stability and resistance to chemical attacks over polymer based thin film humidity sensors. The disad- vantage of ceramic based sensors is that they require initial heating to remove contaminants such as oil and dust. Organic polymers based sensing materials on the other hand, can operate effectively at room temperatures and are cost-effective, easy to fabricate and have good sensitivity. However, organic polymer based sensors suffer from long term drift, low water-durability, slow response times and limited operation in harsh environments. To address the aforesaid issues, hybrid inorganic-organic materials have gained https://doi.org/10.1016/j.sna.2019.111574 0924-4247/© 2019 Elsevier B.V. All rights reserved.