Fabrication of Bi-doped In2S3 thin films for highly sensitive UV photodetector applications

Abstract

Fabrication of highly sensitive, high-speed photodetectors, especially using cost-effective and less toxic materials, has attracted continuous attention due to their outstanding advantages. In this report, we present different properties of Bi-doped (0,1, 3, and 5 wt%) In2S3 thin films for UV photodetectors. Bi-doped (0, 1, 3, and 5 wt%) In2S3 thin films were coated on glass substrates at a temperature of 350 °C using a low-cost nebulizer spray pyrolysis method. X-ray diffraction XRD analysis confirmed the cubic phase β-In2S3 for all the deposited films and high crystallinity is obtained for 1 wt% Bi-doped film. The presence of densely packed grains in 1 wt% Bi-doped In2S3 thin film and also small grains observed for undoped In2S3 sample is evident form morphology studies. Bi doping has caused an enhancement of optical absorption and incorporation of 1 wt% of Bi3+ into In2S3 has shifted the optical band gap from 2.87 to 2.78 eV. Current − Voltage characteristics and Current–Time characterization are used to know the key parameters of the photodetectors. Among all fabricated photodetectors, the In2S3 thin film doped with 1 wt% Bi showed superior photodetector performance with calculated Responsivity (R), Detectivity (D*), and External quantum efficiency (EQE) values of 0.65 AW−1, 15 × 1010 Jones, 125 % respectively. Transient photo-response analysis showed low rise and fall time of 3.21 and 3.78 s respectively for the 1 wt% Bi-doped sample. Optimally doped In2S3: Bi (1 wt%) thin film is most suited to fabricate photo sensing-based optoelectronic devices in UV region of the spectrum.