Thickness-Controlled Transport–Reaction Regime Transition in Perovskite Solar Cells: A SCAPS-1D Dimensionless Flux–Kinetics Framework

Abstract

The integration of photovoltaic devices with surface-driven chemical processes offers a promising pathway for sustainable energy conversion. However, conventional modeling approaches typically treat charge transport and reaction kinetics independently, limiting the identification of performance bottlenecks in coupled systems. In this work, a transport–reaction framework is developed to directly link photovoltaic charge transport with surface reaction kinetics. A SnO₂/CsPbI₂Br/CuI perovskite solar cell is simulated using SCAPS-1D, and the electron flux (Φₑ) is extracted from the maximum power point current density. A dimensionless coupling parameter, Φ = Φₑ/k, is introduced to quantify the balance between charge supply and reaction demand. The results reveal a transition from reaction-limited (Φ ≫ 1) to transport-limited (Φ ≪ 1) regimes at Φ = 1. The electron flux imposes an upper bound on sustainable reaction rates, with a critical transition occurring at k ≈ 10¹⁶–10¹⁷ s⁻¹. This behavior is analogous to a Damköhler-type scaling, highlighting the competition between transport and reaction processes. The proposed framework provides a generalizable framework for optimizing coupled photovoltaic–reaction systems.