Novel Nd-doping effect on structural, morphological, optical, and electrical properties of facilely fabricated PbI2 thin films applicable to optoelectronic devices

Abstract

Lead iodide is one of the best room temperature radiation detector including applications in solar cell and photodetectors. Herein, we have fabricated the high-quality thin films of pure and Nd:PbI2 through a simple and cost-effective spin-coating route and investigated their key properties. X-ray diffraction study confirms the growth orientation of all films along c-axis/(001) plane and single phase of 2H-PbI2 Polytypes with the crystallites of size in range of 21–31 nm. Further confirmation of growth and phase was carried out through FT-Raman analysis. EDX and SEM mapping was also carried out to confirm the Nd doping and its homogeneity in the films. SEM provides a clear view on the surface morphology of grown films and grain size was found in the range of 54–71 nm. Optical measurement shows high transparency, i.e., ~ 90% for grown films in visible to NIR region. The direct bandgap is observed to be enhanced with Nd doping from 2.45 to 2.58 eV; however, there is another bandgap which shows reduction with doping from 2.30 to 2.24 eV. This shows the possibility of existence of sub-energy bandgap in PbI2. The stable value of refractive index is evaluated ~ 2. The value of eʹ is found to varies from 4 to 27 in the energy range of 1–2.5 eV. Optical limiting behavior of all films was also studied at two lasers of λ = 532 nm and 632.8 nm. Moreover, a device fabrication was done for electrical study and found the resistivity increases from 5.14 × 108 Ω-cm for pure to 1.18 × 109 Ω-cm for 5% Nd-doped PbI2.