Influence of Pore Size on the Optical and Electrical Properties of Screen Printed TiO2 Thin Films

Abstract

InfluenceofporesizeontheopticalandelectricalpropertiesofTiO2 thinfilmswasstudied.TiO2 thinfilmswithdifferentweight percentages(wt%)ofcarbonblackweredepositedbyscreenprintingmethodonfluorinedopedtinoxide(FTO)coatedonglass substrate. Carbon black decomposed on annealing and artificial pores were created in the films. All the films were 3.2𝜇m thick as measured by a surface profiler. UV-VIS-NIR spectrophotometer was used to study transmittance and reflectance spectra of the films in the photon wavelength of 300–900nm while absorbance was studied in the range of 350–900nm. Band gaps and refractiveindexofthefilmswerestudiedusingthespectra.Reflectance,absorbance,andrefractiveindexwerefoundtoincreasewith concentrationsofcarbonblack.Therewasnosignificantvariationinbandgapsoffilmswithchangeincarbonblackconcentrations. TransmittancereducedastheconcentrationofcarbonblackinTiO2 increased(i.e.,increaseinporesize).Currentsandvoltages (𝐼-𝑉)characteristicsofthefilmsweremeasuredbya4-pointprobe.Resistivity(𝜌)andconductivity(𝜎)ofthefilmswerecomputed fromthe 𝐼-𝑉 values. It was observed that resistivity increased with carbon black concentrations while conductivity decreased as theporesizeofthefilmsincreased.