2D MoS2–carbon quantum dot hybrid based large area, flexible UV–vis–NIR photodetector on paper substrate

While all reports on 2D–0D hybrid photodetectors are on silicon substrate and based on heavy metals quantum dots exhibiting limited range detection, this paper is the first demonstration of 2D MoS2–carbon quantum dot (CQD) based flexible broadband photodetector (PD) wherein MoS2 was grown on cellulose paper using hydrothermal method and CQD was synthesized using a low cost, one step pyrolytic process of chia seeds. The absorbance of CQD in UV region combined with the broadband absorption of MoS2 in visible and NIR region broadens the absorbance range. Structural characterization revealed few layered MoS2 and CQD to be in the range of 2–6 nm. Responsivity for the fabricated sensor was found to be 8.4, 2.62 and 18.12 mA/W in UV, NIR and visible region respectively which are comparable and even better compared to photodetector fabricated using sophisticated cleanroom techniques. The PD showed negligible variation in photoresponse under repeated (up to 500 cycles) bending conditions. Discrete distribution of CQD over MoS2 creates unipolar junctions which helps in generation of small local electric fields thereby increasing the sensitivity of the sensor. The work presented here is a major step ahead in fabrication of low-cost flexible broadband photodetectors which finds potential applications in the field of flexible and wearable electronics, security and surveillance systems, etc