Electrically Tunable Solution-Processed Transparent Conductive Thin Films Based on Colloidally Dispersed ITO@Ag Composite Ink

Abstract

Silver (Ag) introduced colloidal Sn-doped In2O3 (ITO) ink for transparent conductive electrodes (TCEs) was prepared to overcome the limitation of colloidally prepared thin film; low density thin film, high resistance. ITO@Ag colloid ink was made by controlling the weight ratio of ITO and Ag nanoparticles through ball-milling and fabricated using spin coating. These films were dried at 220 °C and heat-treated at 450–750 °C in an air atmosphere to pyrolyze the organic ligand attached to the nanoparticles. All thin films showed high crystallinity. As the thermal treatment temperature increased, films showed a cracked surface, but as the weight percentage of silver increased, a flattened and smooth surface appeared, caused by the metallic silver filling the gap between the nano-particles. This worked as a bridge to allow electrical conduction, which decreases the resistivity over an order of magnitude, from 309 to 0.396, and 0.107 Ω·cm for the ITO-220 °C, ITO-750 °C, and ITO@Ag (7.5 wt.%)-750 °C, respectively. These films also exhibited >90% optical transparency. Lowered resistivity is caused due to the inclusion of silver, providing a sufficient number of charge carriers. Furthermore, the work function difference between ITO and silver builds an ohmic junction, allowing fluent electrical flow without any barrier.

Elucidating the effect of Ag interlayer formation on the intrinsic mechanical properties of free-standing ITO/Ag/ITO thin films

“…At the initial stage of the Ag film formation, discontinuous Ag islands are formed according to the Volmer–Weber growth mode, which is known to have a negative effect on conductivity owing to the comparable thickness to the electron mean free path (MFP). 54 As the deposition progresses, these islands grow and percolate to form a semicontinuous/conductive film, thereby the sheet resistance significantly decreases. To select an efficient TCE, the figure of merit is a key parameter that represents the optical and electrical performance of a film.…”

Multifunctional Zn-Doped ITO Sol–Gel Films Deposited on Different Substrates: Application as CO2-Sensing Material

“…The sensors can also detect humidity [29,30]. For these applications, the films were optimized by controlling various parameters such as the annealing temperature [31][32][33][34], substrate type [35][36][37][38], deposition method [39][40][41][42][43], and doping [44][45][46][47][48]. Regarding the deposition method, the ITO thin films were most frequently prepared using physical methods.…”