LAUSR

Abstract A time-dependent approach has been developed for modeling the degradation and recovery rate of short-circuit current density in thin film and perovskite solar cells. A set of six different equations has been derived by fundamentally relating the carrier collection efficiency to the defect/trap creation/annihilation kinetics. The distribution and concentration of defects or traps across the absorber layer of a cell vary under aging conditions. As a result, the carrier collection efficiency changes due to distorted diffusion length and depletion width at the junction. These parameters are both related to defect/trap densities by reverse square 1/ N ( t ) . We applied our modeling on the experimental data reported in the literature on degradation/recovery of CdTe, CIGS, CZTS and perovskite solar cells with various architectures and prepared through different fabrication details. These devices were aged under elevated temperature, prolonged irradiation or moisture. The aging effect was taken as a change in shallow/deep defect density or trap density at mid-gap. A good fit has been obtained by setting fitting parameters in a reasonable range. These include the initial defect density, N 0 , and degradation time constant, τ 0 , of a typical defect increment profile given by N ( t ) = N 0 (1 + t/t0)1/2θ. It was shown that opposite to conventionally believed, the defect density variation may significantly change the current density of the cell even if the absorber layer's thickness is kept constant. This has been occasionally observed by aging techniques using different stress conditions.