Tuning of TCO properties of ZnO by silver addition

• Ag–ZnO films were prepared by spray pyrolysis technique.
• Films having different compositions showed various surface morphologies.
• The low temperature conduction corroborates the optical measurements.
• Films having a composition of 1 wt.% Ag showed a good transparency.
• Band-gap of Ag–ZnO films decreased from 3.21 eV up to 2.97 eV.

In this work, we explore the influence of Ag dopant concentration (i.e. 0–2 wt.%) on the opto-electric properties of Ag doped ZnO thin solid films synthesized by chemical spray pyrolysis technique. Several analytical tools such as XRD, AFM, SEM and dc-two probe technique were used. Structural studies reveal that with increasing the doping level, more dopant atoms occupy the zinc lattice sites but after a certain level, they form neutral defects and become ineffective as dopant impurities. 1 wt.% of Ag doping was the optimum for enhancing electrical conduction and beyond that the distortion caused in the lattice inhibits further conduction. Distinct changes including a red shift and narrowing of band gap with increasing Ag content was observed. The low temperature conduction has been explained by variable range hoping (VRH) mechanism. The possible distribution of Ag in the Ag–ZnO thin films has been tentatively discussed.

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