Photomechanically accelerated degradation of perovskite solar cells†

Abstract

Understanding the origin of intrinsic instability of metal halide perovskites is indispensable for their advancement in opto-electronic applications. Here, we report a photomechanically accelerated degradation mechanism of perovskite thin films, in which the lattice expansion driven by light illumination has been found to govern the degradation kinetics. The dynamic lattice evolution under illumination causes crowding of the perovskite grains, leading to large local strains near the grain boundaries (GBs), which thereby facilitates defect formation and iodine component loss in the region. We show that the physical separation of each perovskite grain using trans-polyisoprene (TPI) could circumvent photomechanical damage at the GBs, achieving a T₉₇ of 1000 h under continuous one-sun illumination at 55 °C in solar cell devices. Our results emphasize the nontrivial role of dynamic lattice deformation in the decomposition of perovskite thin films and open up new possibilities to further improve the intrinsic stability of solar cells.