Steady-State Carrier Distribution under Short-Circuit Conditions—Role of Electric Field and Generation Rate Profiles in homo-pn Solar Cells

Short-circuit current density (JSC) represents the maximum extractable current for photovoltaics, and closing the gap to its radiative limit is crucial for advanced and emerging technologies. However, analysis of its losses remains unstructured, because the classical current density expression—proportional to carrier concentration and gradient of quasi-Fermi levels—becomes cumbersome under short-circuit conditions. Most simulations therefore focus on the maximum-power point, leaving no clear framework for pinpointing JSC losses or developing design guidelines. Here, we address this issue using a charge-balance framework, in which the divergence of current density equals the net generation at steady state. This formulation reduces the analysis of JSC to identifying the dominant factors governing the excess carrier distribution under short circuit conditions—an approach that constitutes the main contribution of this work. Systematic SCAPS-1D simulations of homo-pn solar cells reveal that this distribution is governed primarily by the internal electric field, rather than the equilibrium carrier concentration, although both drift and diffusion contribute. Analysis using infinitesimal photogeneration slices further shows that each excess carrier distribution consists of a peak at the generation site and tails extending into nongeneration regions, both of which drive recombination. This framework offers a direct, quantitative route for identifying and minimizing JSC losses.