High quality semiconductor Cd2SnO4 films for solar cell applications

Abstract

In this work, we study the effect of Ar/CdS annealing treatment on physical properties of semiconductor Cd2SnO4 (∼260 nm thick) films. The films were produced by sol–gel dip-coating method and annealed at 450 °C ≤ T a ≤ 650 °C. A full characterization of the optical, electrical, and structural properties, and a discussion of the mechanism that yield enhanced physical properties is presented. All annealing treatments explored led to the improvement of physical properties of the semiconductor films. However, values of electrical resistivity of 6 × 10−4 Ω-cm, carrier concentration of 3 × 1020 cm−3 and mobility of 35 cm2 Vs−1 were reached at T a = 650 °C, without compromising the optical properties (T ≥ 85% for 450 ≤ λ ≤ 1200 nm). These represent an improvement of almost 6-fold over untreated films. Although the Moss–Burstein effect leads to a band gap of 3.5–3.7 eV, the fundamental band gap was estimated to be 3.3 eV. Moreover, the computed work function, 4.7–4.4 eV, indicates that these films can be used as transparent conductive oxide to design high-efficiency CdS/CdTe thin-film solar cells due to the smooth match of Fermi level with CdS coupled layer.