Investigation of the transparent conducting properties of spray-pyrolyzed Li and F co-doped SnO2 thin film electrodes

Transparent conducting electrodes (TCEs) with high electrical conductivity and optical transmittance form an inevitable component in optoelectronic devices. Undoped SnO2 and Li (0 to 3 wt%): F (5 wt%) co-doped SnO2 films were deposited onto glass substrates using spray pyrolysis technique and are explored as alternative TCEs. Film crystallinity is found to improve upon codoping with Li and F. Granular surface morphology is observed in the deposited films and least surface roughness of 25.1 nm is observed for Li (1 wt%): F (5 wt%) co-doped SnO2 thin film. The direct optical bandgap values of the films estimated using Tauc plot are in the range 3.02-3.21 eV. The Li (1 wt%): F (5 wt%) co-doped SnO2 thin film exhibits highest average optical transmittance around 90% at 550 nm. Photoluminescence emission measurements indicate the presence of oxygen vacancy defects which are estimated using Smakula's formula. The observed variation in sheet resistance is attributed to replacement of Sn atoms at the cationic sites in addition to the F atoms occupying the anionic sites, thereby creating deep donor levels. The high figure of merit value (378 x 10(-6) Omega(-1)) indicates improved balance between transmittance and sheet resistance for Li (1 wt%): F (5 wt%) co-doped SnO2 film. The observed results advocate further exploration of the properties of Li:F co-doped SnO2 thin films toward potential alternative TCE system.

Automated summary

Transparent conducting electrodes (TCEs) with high electrical conductivity and optical transmittance are essential components in optoelectronic devices. Undoped and Li:F co-doped SnO2 films were deposited on glass substrates and showed improved crystallinity and high optical transmittance. The co-doped SnO2 film with Li (1 wt%): F (5 wt%) exhibited the highest figure of merit value, indicating a balance between transmittance and sheet resistance. Further exploration of these properties is recommended for potential alternative TCE systems.