Theoretical Analysis and Design of Microphotodiodes Material for Artificial Retina Implant

As a typical member of two-dimensional TMDs, molybdenum disulfide (MoS2 ) has excellent carrier mobility, a sizable surface area, thermal stability, and optoelectronic features. Due to its tunable bandgap, strong valence–conduction band bonding, and use in optoelectronic sensors, photodiodes, and phototransistors, MoS2 has emerged as a possible substitute for graphene. For better optoelectronic properties, MoS2 -based monolayers and crystals have recently been investigated using a variety of heterostructures, including MoS2 /graphene, MoS2 /CNT and MoS2 /WS2 . It was also mentioned that MoS2 phototransistors and sensors had poor light sensitivity because of their insufficient ability to absorb light. The right choice of material is essential for biomedical implants, including retinal implants, neuroprosthetic implants, and others where photodiodes are used to generate electrical currents in reaction to incident light Au-based nanoparticles and nanoarrays have been added to the MoS2 monolayer to address the low absorption problem. For increased quantum efficiency, MoS2 monolayers based on solar cells and light-emitting diodes have also recently been created. In some of the other research, other transition metal (TM) atoms, such as Au, Ag, Cu, Nb, Tc, Ta, Re, Co, Ni, Fe, and Mn, were substituted into the monolayer of MoS2 , enhancing the material's electrical, magnetic, electrocatalytic, and gas adsorption capabilities. The combined electrical and optical properties of TM-doped and alkaline metal (AM) doped MoS2 bulk layers haven't received much attention, though. In this study, the effects of doping MoS2 bulk layers with TM atoms (Au, Ag, and Cu) and AM atoms (Na, Li) were investigated using first-principles DFT calculations. We investigated the density of states (DOS), band structures, structural features, optical conductivity, absorption, and reflectivity of five different doped MoS2 bulk layers. The results show that AM atom doping narrows the MoS2 bulk layer's bandgap more than TM doping. Bandgap values ranged from 1.42 eV for the undoped MoS2 layer to 0.609 eV for the Li-MoS2 layer. Additionally, it was discovered that bulk layers of MoS2 doped with AM had higher optical conductivity and absorption qualities and lower reflectivity. In applications of MoS2 - based photodiode/phototransistor sensors, doping of AM atoms may show to be a successful substitute for conventionally used TM (Au) doped arrays.

Keywords: Absorption, Artificial vision, Conductivity, Density Functional Theory, Dielectric coefficient, Reflectivity.