Simulation of ferroelectric domains and grain boundaries in perovskite solar cells (Conference Presentation)

This work is focused on understanding the role that ferroelectric domains in methylammonium lead halide perovskite (MAPbI3) on the one hand and grain boundaries on the other can have on the performance of solar cells built from this material. We study 2D and 3D systems considering different polarization domain patterns, inspired by measurement data, by proposing a polarization model based on the knowledge of the crystalline structure, symmetry considerations and electrical simulations. Structures with grains are constructed from SEM data. We compute charge carrier transport by solving a drift-diffusion model, in which the Poisson equation for the electrostatic potential calculation explicitly includes the polarization field. The effects of grain boundaries are simulated by considering different types of trap states at the boundaries. We show that the presence of polarization domains has a strong impact on charge separation, thus leading to a decrease of recombination losses and formation of current pathways at domain interfaces. Specifically, the decrease of Shockley-Read Hall recombination losses improves the open-circuit voltage, while the low resistivity current pathways lead to improved transport and an increase of the short-circuit current. The achieved results demonstrate that the presence of ordered ferroelectric domains, even with weak magnitude of polarization, can actually affect the performance of the solar cell in terms of enhanced power conversion. Moreover, from the comparison between our results and experimental IV characteristics of MAPb(I,Cl)3 devices we conclude that the polarization model proposed can effectively reproduce the solar cell operation.