A design and modeling perspective on photostimulation of the subretinal prosthesis with graphene-based photodiodes

The two leading causes of blindness in the developed world are age-related macular degeneration and retinitis pigmentosa. The photostimulation of remaining retinal neurons using a photodiode in a proposed subretinal prosthesis is one of the solutions that hopes to restore vision. In this paper, we envision a better result through device simulation and modeling of a graphene-based photodiode that yields high-performance, wire-free, and light-induced retina implants. This study shows how the characteristics of graphene-based photodiodes have an improved result in terms of low threshold requirements for the activation of neurons. Graphene-based photodiode responsiveness is significantly improved in the visible and near-infrared ranges. Using a graphene photoconductive layer in a silicon photodiode can significantly decrease contact resistance, reduce dark current up to 20-fold, and lower the induced thermal effect and spontaneous emission by orders of magnitude of 10³ and 10⁶, respectively, compared to its Si counterparts. This advancement highlights graphene’s potential for optimizing metal–semiconductor interfaces, offering improved precision and sensitivity for high-resolution retinal prosthesis applications requiring enhanced signal-to-noise ratio and finer control. We offered a range of sizes for graphene-based photodiode arrays, including [5 × 5], [6 × 6], [6 × 7], and [7 × 6], to ensure the subretinal prostheses meet thermal safety standards. Physics-based modeling and simulation of graphene-based devices help us understand charge transfer mechanisms, improve operating bias, and achieve proper band gap modulation, which ushers in the development of graphene-like 2D materials for photostimulating neurons in projected retinal prostheses.