Toward Understanding the Short-Circuit Current Loss in Perovskite Solar Cells with 2D Passivation Layers

Herein, a strong short-circuit current density (J(SC)) loss is observed when using phenetylammonium iodide (PEAI) as n-side passivation in p-i-n perovskite solar cells. Comparing experiments with drift-diffusion simulations, different hypotheses for the origin of the J(SC) loss are presented and evaluated. Whereas the optical properties of the investigated cell stack remain unchanged, the internal quantum efficiency of the PEAI-based devices decreases drastically. Strong bulk doping and interface traps are ruled out as the origin of the charge extraction limitation. High-spatial resolution photoluminescence (PL) spectroscopy directly images the inhomogeneity of the PEAI-based quasi-2D perovskite wide-bandgap interlayer, which is found to be crucial for the observed J(SC) loss. A 2D drift-diffusion model implemented with mobile ions and an inhomogeneous electron transport layer reproduces the experimental behavior accurately. The ionic space charge distribution under short circuit reduces the effective charge-carrier diffusion length, hindering charge transport toward those domains in the perovskite-electron transport layer interface where electrons can be extracted efficiently. A longer charge-carrier lifetime reduces the J(SC) loss, highlighting the importance of suppressed non-radiative bulk recombination, not only for achieving high open-circuit voltages, but also for efficient charge extraction.