We report the first synthesis of colloidal lead iodide PbI 2 nanoparticles by pulsed laser ablation in methanol. Structural and optical properties of PbI 2 nanoparticles were investigated. The optical absorption data showed three distinct absorption peaks (Plasmon) at 220, 250 and 302 nm, with a direct optical band gap of 2.82 eV. X-ray diffraction XRD analysis revealed that the synthesized PbI 2 nanoparticles were polycrystalline in nature with hexagonal phase. Transmission electron microscope (TEM) investigation displayed (18-40 nm) spherical PbI 2 nanoparticles. The electrical and photo-response characteristics of PbI 2 nanoparticles/n-Si heterojunction were measured and analyzed.
The effect of deposition environment conditions on the electrical and structural properties of deposited PbI 2 layers were studied. The layers were deposited from solution under dark and room light illumination with and without applying magnetic field. XRD, electrical, and photo-electrical properties were measured at room temperature. An increase in the grain size versus the platelet area was noticed.The electrical properties revealed a dependence on deposition conditions. Dark conductivity increases from 1.7×10 −10 to 5 × 10 −9 (Ωcm) −1 when deposition was carried out in darkness. A gain factor (the ratio between photoconductivity and dark conductivity) of (23) was obtained. The results indicate that the increase in electrical conductivity is mainly due to the plane 001, where the average number of grain boundaries in this plane sharply decreases when deposition takes place in darkness. On the other hand, the increase in photoconductivity could be due to the decrease in the recombination of free carriers along the grain boundaries.
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