Investigation on visible spectral response of spray coated Ni doped CuGaS2 thin films for photodetector application

Abstract

The visible light spectrum attracts vast interest in photodetector applications and takes an integral part in image sensing and communication. Ternary chalcopyrite, such as CuGaS2 can be used for visible light detection owing to its higher light absorption coefficient and wider bandgap. This work presents pristine and Nickel-doped CuGaS2 (0.5, 1.0, 1.5 wt. %) thin film photodetectors prepared by the low-cost Chemical Spray Pyrolysis technique. Structural analysis confirms the formation of the pure CuGaS2 phase and the evidence of Ni inclusion inside the lattice. The optical bandgap of the Ni-doped CGS thin films was reduced compared with pristine CuGaS2, leading to higher absorption in the visible region. The interaction of photons with CuGaS2 and its photoconductive mechanism is probed through photoresponse studies. The responsivity and detectivity were calculated for all the photodetectors under constant bias (1V) and power density (4 mW/cm2). All the devices show excellent photoresponse despite having a higher photosensitive area of 1 cm2 and a very low bias for operation. Particularly, 0.5 wt. % Ni-doped CGS photodetector device showed higher responsivity and detectivity of 1.6 μAW−1 and 19.6 × 106 Jones respectively than others. The admirable optical and electrical properties due to Ni doping played a crucial role in this superior performance. Hence, our investigation suggests Ni-doped CuGaS2 thin films can be employed in the fabrication of thin film photodetector devices.