A one-dimensional solar cell is a computational or physical model in which the photovoltaic device structure and its governing equations are treated as varying only along a single spatial coordinate—usually the depth normal to the illuminated surface—while material properties are assumed uniform in the lateral directions ^[1]. The model solves, along that coordinate, Poisson’s equation for the electrostatic potential coupled to the electron and hole continuity equations and the drift–diffusion current equations, together with optical generation as a function of depth and wavelength ^[2]. Carrier transport, recombination (radiative, Shockley–Read–Hall, Auger), and the resulting current–voltage and quantum-efficiency characteristics are computed under boundary conditions at the front and back contacts ^[3]. The one-dimensional approximation reduces a multilayer thin-film or crystalline device to a stack of homogeneous layers and is the conceptual basis of standard solar-cell simulators, distinguishing it from two- or three-dimensional models that resolve lateral fingers, shunts, and microstructural inhomogeneities ^[4].