Thermally reduced solution-processed graphene oxide thin film: An efficient infrared photodetector Farzana A. Chowdhury a , Tomoaki Mochida b , Joe Otsuki b , M. Sahabul Alam c,⇑ a Experimental Physics Division, Atomic Energy Centre, 4, Kazi Nazrul Islam Avenue, Dhaka 1000, Bangladesh b College of Science and Technology, Nihon University, 1-8-14 Kanda Surugadai, Chiyoda-ku, Tokyo 101-8308, Japan c Department of Physics, Faculty of Science, University of Dhaka, Dhaka 1000, Bangladesh article info Article history: Received 30 November 2013 In final form 9 January 2014 Available online 15 January 2014 abstract A sharp response of infrared light detecting capability is observed in reduced graphene oxide based pho- todetector. The photoresponse increased with increasing solution concentration and annealing duration, at a low percolation. The photocurrent increases considerably before saturation and persists for a maxi- mum time of 26 min. This Letter also reports on superiority of device performance with continuous annealing over annealing with an interval. A maximum photoresponsivity of 0.55 A/W and external quantum efficiency of 57% was achieved at low power light intensity (0.8 mW/cm 2 ). This Letter presents an efficient graphene oxide thin film infrared photodetector processed via a modified synthesis protocol. Ó 2014 Elsevier B.V. All rights reserved. 1. Introduction Graphene, a two dimensional atomically thin carbon material and its derivative like graphene oxide (GO) have attracted much attention due to its remarkable electronic [1,2] and optical proper- ties [3]. Their applications in nano-electronics, nano-sensors and nano-bio engineering are of great interest in the industry [4,5]. Infrared (IR) detection is a primary subject in optical sensing and is vital for a variety of military and scientific applications, including monitoring and controlling manufacturing process, optical com- munication, etc. [6–8]. In the last decade, the synthesis and charac- terization of one-dimensional nanostructure of graphene, and its derivatives GO have been attracting special scientific and techno- logical attention as future candidates for optoelectronic device applications, as for example, photodetector [9–11]. Pristine graph- ene-based photodetectors have high performance in high fre- quency devices but their photoresponsivity is quite low due to the fast carrier dynamics and low light absorption by single layer grapheme [12]. Chemically converted graphene (GO) is therefore expected to have strong photoresponse behavior due to its tunable electronic property [13]. GO is a layered material consisting of hydrophilic oxygenated graphene ribbon sheets containing oxygen functional groups on their basal planes and edges [14,15]. The as- prepared GO films are electrically insulating due to the heavy oxy- genation of graphene sheets [16–19] but could be made conductive by thermally or chemically into reduced graphene oxide (RGO) to facilitate the carrier transport more efficiently [16,17]. Although hydrazine is most widely used as a chemical reductant, its toxicity and explosiveness pose a problem [18]. To develop carbon-based cheap optoelectronic devices with excellent performances, it is vi- tal not to use toxic chemicals [10]. Besides this, hydrazine is not ideal to control the extent of reduction because of the first kinetics [19]. As thermal reduction has been performed only at high tem- peratures (300–1100 °C) [19], a low processing temperature is highly desirable for making it useful in practical applications [18]. Furthermore, the enhancement of photodetection capability as well as cost reduction is of great concern in the fabrication of low dimensional structures in modern nanoscience related tech- nologies. Recently, a cost effective practical route to grow device quality thin films on glass by a simple solution casting process at low percolation temperature without using reagent has been re- ported [18]. In this report, we demonstrated the tunability of the optoelectronic properties of solution processed GO. A systematic investigation on different growth conditions and their effects on the infrared photodetector are necessary to find a straightforward scalable technique with an efficient performance i.e., higher photo-current, high efficiency, long term retention of the photocurrent and so on. Besides these, large-area thin-film deposition of GO, facilitated by its solubility in a variety of solvents, tenders a direction towards GO-based thin-film electronics and optoelectronics [17]. These extraordinary properties are appealing for cost reduction in device fabrication process. The photoresponse performances of pristine graphene based photodetector devices have already been reported [20–23]. On the basis of mechanically exfoliated single- and few-layer graph- ene, a high frequency, ultrafast 40 GHz photodetector has been fabricated and reported [23]. The authors found an intrinsic bandwidth of more than 500 GHz. Even though pristine graph- ene-based photodetectors have demonstrated high frequency 0009-2614/$ - see front matter Ó 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.cplett.2014.01.012 ⇑ Corresponding author. Fax: +880 2 8615583. E-mail address: alam@univdhaka.edu (M.S. Alam). Chemical Physics Letters 593 (2014) 198–203 Contents lists available at ScienceDirect Chemical Physics Letters journal homepage: www.elsevier.com/locate/cplett