## 1 Introduction  
Thin film (TF) materials with high transmittance as well as low electrical resistance have been spotlighted by researchers who may realize next-generation opto-electronic devices, such as displays, solar cells, touch panel, light-emitting diodes, etc [1; 2; 3; 4]. Typically, tin-doped indium oxide (ITO) TF has been used as a transparent electrode; however, its use will be limited due to the scarcity, toxicity, and low stability of indium [5; 6; 7]. ZnO is a direct transition-type semiconductor material with a band gap energy of 3.3 eV, and it has a large exciton binding energy of 60 meV even at room temperature. These qualities suggest that it could be considered as a potential alternative material for ITO due to its transparency, non-toxicity and cost-efficiency [8; 9].  
However, ZnO TF has a relatively high electrical resistance that restrains the wider use of ZnO. In order to reduce the electrical resistance of ZnO, many researchers have been using cation doping against the Zn site. [PERSON] et al. modified the physicochemical properties of ZnO to improve the performance via Al doping [10], and [PERSON] et al. prepared Ga-doped ZnO to increase electrical conductivity [11]. It was revealed that ZnO TF doped with group-III elements (B, Al, Ga, In) exhibited low resistivity and high transparency in the visible region. Because of the similar covalent bonding lengths of Zn-O and Al-O, Zn\({}^{2+}\) ions in the ZnO matrix can be structurally stable even when substituted with Al\({}^{3+}\), and electrical conductivity can be improved by increasing charge carriers [12; 13; 14]. Nevertheless, the electronic transport behavior of Al-doped ZnO (AZO) TF is largely influenced by grain boundary scattering in electronic transmission because it consists of crystallization of several nanoscale sizes.  
Recently, hybrid nanostructure technologies with carbon-based composites have been applied to overcome the mechanical, chemical, electrical, and opto-electronic properties [15; 16; 17; 18; 19; 20]. Among the diverse carbon nanomaterials, reduced graphene oxide (RGO) has been considered as one of the most attractive material for next-generation electronics since it has high charge carrier mobility originating from a two-dimensional (2D) atomic structure of carbon with sp\({}^{2}\) hybridization [21; 22; 23]. In this study, we focus on the effect of graphene on the charge transport behavior in the AZO-RGO nanocomposite (NC) TF. The AZO-RGO nanocomposite thin film (NCTF) was deposited on a SiO\({}_{2}\)/Si substrate using the electrospray deposition process with RGO-dispersed precursor solution. Compared to the pristine AZO TF, the AZO-RGO NCTF shows enhanced mobility resulting from an increase in carrier concentration. Grain boundary scattering could be suppressed due to the Schottky barrier reduction with RGO incorporation between the grain boundary, resulting in an increased charge transport behavior in the AZO-RGO NCTF. Therefore, we provide a facile strategy to fabricate advanced transparent conducting film by incorporating RGO on AZO TF, and this nanocomposite TF could be a practical form of technology for controlling electronic transport behavior for various opto-electronic applications.