Non-destructive evaluation of carrier transport properties in CuInS2 and CuInSe2 thin films using photothermal deflection technique

Photothermal deflection technique (PTD) is a non-destructive tool for measuring the temperature distribution in and around a sample, due to various non-radiative decay processes occurring within the material. This tool was used to measure the carrier transport properties of CuInS₂ and CuInSe₂ thin films. Films with thickness < 1 μm were prepared with different Cu/In ratios to vary the electrical properties. The surface recombination velocity was least for Cu-rich films (5 × 10⁵ cm/s for CuInS₂, 1 × 10³ cm/s for CuInSe₂), while stoichiometric films exhibited high mobility (0.6 cm²/V s for CuInS_2, 32 cm²/V s for CuInSe₂) and high minority carrier lifetime (0.35 µs for CuInS₂, 12 µs for CuInSe₂).