Abstract:
The present work is based on the deposition of thin films of transparent conductive oxide
(TCO) films of zinc oxide (ZnO) and aluminum doped zinc oxide (Al:ZnO) using sol gel
spin coating method for the application in thin films based solar cells such as
Cu(In,Ga)Se2. The precursor zinc acetate dihydrate (Zn(CH3COO)2.2H2O) was dissolved
in isopropanol ((CH3)2CHOH) with monoethanolamine ((HOCH2CH2)NH2) added as
stabilizer. Various chemical and processing parameters such as coating thickness, additive
ratio, sol concentration, effect of annealing and dopant concentrations were investigated in
order to find best combination of films regarding their electrical resistivity and optical
transmittance. X-ray diffractrometer (XRD) and scanning electron microscopy (SEM)
analysis were used to investigate the crystallinity and surface morphology of the films.
Hall Effect Measurement System was used to find resistivity, carrier mobility and carrier
density of deposited films. Optical transmittance was investigated using
spectrophotometer. In case of intrinsic ZnO films, lowest resistivity of 1.97×102 Ω.cm was
shown by films grown using 0.2M sol, annealed at 500 ᵒC for one hour which further
decreased to 4.06×10-3 Ω.cm when the films were doped with 1 at. % aluminum. Films
with dense granular morphology and preferential texturing in (002) direction were
deposited. The optical studies reveal absorption edges at ∼370 nm. The optical band gap
energy was calculated to be in range of 3.2-3.5 eV. Transmittance was greater than 80% in
the visible region for all deposited films.
