Enhanced Performance of Al-Doped ZnO through <i>In Situ</i> Pressure-Controlled Growth: An Alternate Approach for Developing n-Type Transparent Conducting Materials for Optoelectronic Devices

Transparent conducting materials exhibit a unique combination of high electrical conductivity and high optical transparency within the visible range, two seemingly impossible properties to be present in any solid-state material, simultaneously. This uniqueness makes them the backbone of the whole electronic and optoelectronic industries and is currently dominated by indium-based materials. High-performance aluminum-doped zinc oxide (AZO) nanocrystals could be a viable option for application in transparent electronics. This work focuses on the impact of in situ pressure on the AZO nanoparticles in driving their optoelectronic properties, which is being reported for the first time to the best of our knowledge. Thin film fabricated with AZO nanoparticles synthesized at 100 bar of pressure (AZO-100) has the highest figure of merit, optical transparency (>95%) and lowest sheet resistance (∼103 Ω sq–1), significantly lower than the AZO film fabricated from the nanoparticles synthesized at atmospheric pressure. These modifications could be attributed to the improved crystallinity, lowering of surface roughness, and shifts in band gaps, which facilitate electron transfer, as is evident from the optical and valence-band electronic structure measurements, suggesting a substantial influence of in situ pressure-controlled growth of AZO nanoparticles. The improved properties confirm the possibility of using AZO-100 as an n-type transparent conducting material, replacing indium tin oxide in various optoelectronic devices, as successfully demonstrated in laboratory-fabricated prototype liquid crystal display (LCD) and organic light-emitting diode (OLED) devices using the developed films.