Synthesis of Colloidal CsHgI3 Nanocrystals by Laser Ablation in Liquid for Organic-Inorganic Photodetectors

This work investigates the structural and optical properties of colloidal suspensions of CsHgI3 nanoparticles synthesized by laser ablation in liquid, prepared at 12.7 J/cm(2) and 33.1 J/cm(2). The x-ray diffraction results confirm the formation of crystalline cubic CsI, tetrahedral and orthorhombic alpha, and beta-HgI2 phases, as well as a peak related to the crystalline CsHgI3. The photoluminescence spectra show the presence of two emission peaks. The transmission electron microscopy images confirm the formation of spherical nanoparticles, and the average particle size increased from 25 nm to 28 nm as laser fluence increased from 12.7 J/cm(2) to 33.1 J/cm(2). The scanning electron microscopy image shows the formation of a spherical nanoparticle morphology for the sample prepared at 12.7 J/cm(2), while the sample prepared at 33.1 J/cm(2) exhibits platelet morphology with the presence of orthorhombic crystals. The energy-dispersive x-ray result for the sample prepared at 33.1 J/cm(2) confirms the formation of stoichiometric CsHgI3. The stability studies of the synthesized nanoparticles reveal that the value of the zeta potential of a sample prepared at 12.7 J/cm(2) was -6 mV and that the sample synthesized at 33.1 J/cm(2) has a zeta potential of 72 mV. The photoluminescence results reveal that the sample prepared at 12.7 J/cm(2) shows two emission bands at 433 nm and 680 nm, while the sample prepared at 33.1 J/cm(2) shows two emission peaks centered at 430 nm and 731.7 nm. The optical properties show that the optical energy gap of the CsHgI3 synthesized at 12.7 J/cm(2) and 33.1 J/cm(2) is 2.98 eV and 3.04 eV, respectively. The current-voltage characteristics of the CsHgI3/Si heterojunction in the dark and under illumination at room temperature are investigated. The responsivity of the photodetector prepared at 12.7 J/cm(2) was 2.65 A/W, while the photodetector fabricated at 33.1 J/cm(2) was 3.17 A/W at 400 nm.