Modeling the dynamics of interacting defects, charge carriers, and excitons in perovskite solar cells

This talk presents calculations based on a theoretical model that includes the dynamics of excitons, free charge carriers, and electrically active defects, to study the stability of perovskite solar cells. Previously, the PVRD-FASP tool was developed and released for public use (www.pvrdfasp.com) to model metastability and reliability issues of solar cells. In the model, charge carriers and electrically active defect centers are treated on an equal footing, as both obey the same reaction-kinetic equations: the continuity, drift-diffusion, and the Poisson equations. The rate terms in these equations are highly non-linear and require solution of a system of stiff partial differential equations. To efficiently solve such systems, a reaction solver based on the forward Euler method implicit in time with a Newton step was proposed and implemented. The Jacobian for the Newton step was analytically calculated. The PVRD-FASP tool was used successfully to study the role of Cu migration in CdTe solar cells. In current work, the theoretical model of the tool is expanded to include the dynamics of excitons. The expanded solver is used to study the stability of perovskite solar cells in the presence of light-induced formation and annihilation of defects acting as carrier trap states.