Influence of Mn content on the optical, structural and electrical properties of spray pyrolysis deposited quinternary Cu2Cd1−xMnxSnS4 thin films for solar cells

Novel quinternary Cu2Cd1−xMnxSnS4 (0 ≤ x ≤ 1) semiconductor thin films were deposited onto soda lime glass substrates at 300 ℃ by the spray pyrolysis technique to study the effect of Mn content on the structural, compositional, topographical, optical, and electrical properties. X-ray diffraction analysis showed that an increase in Mn content in the Cu2Cd1−xMnxSnS4 films resulted in à transition from the cernyite to stannite phase tetragonal crystal structure and a change in lattice parameters. The intensity of the predominant 112 peak was observed to be relatively low at higher Mn content. Energy dispersive X-ray analysis revealed that the Cu2Cd1−xMnxSnS4 films were Cu-poor, Sn-poor and close to stoichiometry. Atomic force microscopy revealed that the average roughness of the films fluctuated between 43.9 and 73.95 nm. Optical characterization showed a high absorption coefficient of 105 cm−1 while the direct optical band gap and Urbach energy varied between 1.79 and 1.92 eV and 226–564 meV, respectively with an increase in Mn content. Electrical resistivity, hole mobility and carrier concentration were observed to fluctuate between 8.5 × 102 and 2.4 × 101 Ωcm, 1.31 × 101–6.24 × 103 cm2/Vs and 2.0 × 107–5.03 × 1013 cm−3, respectively, with an increase in Mn content. The Cu2Cd1−xMnxSnS4 films exhibited a p-type conductivity. The CCMTS can be used as a top absorber layer of tandem solar cells owing to its optical, structural, and electrical properties.