  In terms of mixing graded TiO2 and SnO2 powders by solid-state reaction
method, ITO was prepared. Using electron beam gun technology, ITO films with
different thicknesses were prepared. The influence of film thickness on
structure, electrical and optical properties was studied. The XRD patterns were
utilized to determine the structural parameters (lattice strain and crystallite
size) of ITO with different thicknesses. It is observed that the average
crystallite size increases as the film thickness increases, but the lattice
strain decreases. SEM shows that as the film thickness increases, the grain
size of ITO increases and improves. The electrical properties of ITO films with
different thicknesses were measured by the standard four-point probe method. It
can be seen that as the thickness of the ITO film increases from 75 nm to 325
nm, the resistivity decreases from 29x10^-4 Ohm/cm to 1.65x10^-4 Ohm/cm. This
means that ITO films with lower electrical properties will be more suitable for
high-efficiency CdTe solar cells. Three optical layer models (adhesive layer of
the substrate/B-spline layer of ITO film/surface roughness layer) are used to
calculate the film thickness with high-precision ellipsometry. In the higher
T(lambda) and R(lambda) absorption regions, the absorption coefficient is
determined to calculate the optical energy gap, which increases from 3.56 eV to
3.69 eV. Finally, the effects of ITO layers of various thicknesses on the
performance of CdS/CdTe solar cells are also studied. When the thickness of the
ITO window layer is 325 nm, Voc = 0.82 V, Jsc = 17 mA/cm2, and FF = 57.4%, the
highest power conversion efficiency (PCE) is 8.6%.
