Unveiling facet-dependent degradation and facet engineering for stable perovskite solar cells

Abstract

A myriad of studies and strategies have already been devoted to improving the stability of perovskite films; however, the role of the different perovskite crystal facets in stability is still unknown. Here, we reveal the underlying mechanisms of facet-dependent degradation of formamidinium lead iodide (FAPbI 3 ) films. We show that the (100) facet is substantially more vulnerable to moisture-induced degradation than the (111) facet. With combined experimental and theoretical studies, the degradation mechanisms are revealed; a strong water adhesion following an elongated lead-iodine (Pb-I) bond distance is observed, which leads to a δ-phase transition on the (100) facet. Through engineering, a higher surface fraction of the (111) facet can be achieved, and the (111)-dominated crystalline FAPbI 3 films show exceptional stability against moisture. Our findings elucidate unknown facet-dependent degradation mechanisms and kinetics.

Facet Engineering: A Promising Pathway toward Highly Efficient and Stable Perovskite Photovoltaics

“…In 2023, Park's group further revealed a profound role of different crystal facets in the stability and degradation process of perovskite. 33 As shown in Figure 2f, after exposure to humid air for 200 h, the (111) facets of FAPbI 3 remain intact and undegraded, while the (100) facets seem to degrade and form new small δ-phase protrusions (marked with yellow rectangles). The photocurrent in the region of the (100) facet where the δ-phase is produced drops dramatically from 300 pA to 0, indicating the nonphotovoltaic activity of the δphase (Figure 2g).…”

“…In addition, other methods such as component engineering, additive engineering, and antisolvent engineering can also be able to regulate the crystal orientation to a certain extent, but it seems difficult to achieve quasi-monocrystalline films with a single dominant orientation. 32,33,43,53 A comparison of various regulation methods and their core factors affecting the facet orientation is shown in Table 1.…”

“…In 2023, Park’s group further revealed a profound role of different crystal facets in the stability and degradation process of perovskite . As shown in Figure f, after exposure to humid air for 200 h, the (111) facets of FAPbI 3 remain intact and undegraded, while the (100) facets seem to degrade and form new small δ-phase protrusions (marked with yellow rectangles).…”

“…(g and h) Current and height profiles extracted from the degraded (100) and (111) facets, respectively. Reproduced with permission from ref . Copyright 2023 AAAS.…”

“…This work is a breakthrough of the restrictions on the conventional preferential (001) orientation, expanding the breadth of seeding-induced growth on individually tailored dominant facet orientations. In addition, other methods such as component engineering, additive engineering, and antisolvent engineering can also be able to regulate the crystal orientation to a certain extent, but it seems difficult to achieve quasi-monocrystalline films with a single dominant orientation. ,,, A comparison of various regulation methods and their core factors affecting the facet orientation is shown in Table .…”