Unraveling Photostability of Mixed Cation Perovskite Films in Extreme Environment

Abstract

Organometal halide perovskites exhibit a bright future for applications in solar cells, as efficiency has achieved over 22%. The long‐term stability remains a major obstacle for commercialization. Here, it is found that three cationic compositional engineered perovskites, MAPb(I0.83Br0.17)3, FA0.83MA0.17Pb(I0.83Br0.17)3, and Cs0.1(FA0.83MA0.17)0.9Pb(I0.83Br0.17)3, undergo severe degradation under white‐light illumination in ultrahigh vacuum (UHV) environment, but the rate of degradation is significantly lower for the mixed cation perovskites. This is attributed to the defect‐induced trap states that trigger the strong coupling between the photoexcited carriers and the crystal lattice. The observed behavior supports the view of the mixed cations suppressing the photoinduced degradation. It is further demonstrated that UHV environment remarkably accelerates the degradation of the perovskite films under illumination, which delivers a very important message that the current hybrid perovskite materials and their optoelectronic devices are not suitable for application in outer space. Moreover, the applied UHV environment can be an accelerated test method to estimate the photostability of the perovskites.

Exploring Red, Green, and Blue Light‐Activated Degradation of Perovskite Films and Solar Cells for Near Space Applications

“…For blue light illumination, we note that there are additional peaks at 31.25° and 36.26° emerging that represent the (111) and (002) peaks of metallic Pb, pointing to a decomposition from PbI 2 to Pb, consistent with the XPS results. The photodecomposition processes of the perovskite films in vacuum follow the degradation mechanisms as our previous reports, which are closely related with the numerous defects existing on the perovskite film surface, e.g., impurities, vacancies, and dangling bonds. During light illumination, these large defect trap states capture the photoexcited charge carriers, perturbing the crystal systems and promoting the coupling between the charge carriers and the crystal lattices …”

“…The photodecomposition processes of the perovskite films in vacuum follow the degradation mechanisms as our previous reports, which are closely related with the numerous defects existing on the perovskite film surface, e.g., impurities, vacancies, and dangling bonds. During light illumination, these large defect trap states capture the photoexcited charge carriers, perturbing the crystal systems and promoting the coupling between the charge carriers and the crystal lattices …”

“…More serious phenomena occur for the blue light‐soaked perovskite films, and the original morphological features of the perovskite film fully disappear. As a comparison, the SEM morphologies of the perovskite films exhibit no clear change in the dark in vacuum over 90 h, see Figure S2, Supporting Information, which implies that vacuum has negligible influence on the stability of the perovskite films and light is thus one key factor during the observed degradation . The RGB light illumination induces different degradations of the perovskite films.…”

“…Despite the high device efficiency, solution process at a low cost, and potential for large‐scale manufacturing, the stability of the perovskite solar cells is one major challenge that impedes commercialization . Several factors that affect the stability of hybrid perovskites have been systematically investigated, such as humidity, oxygen, heat, and irradiation .…”

“…Our previous work has unraveled the photostability of perovskite films under prolonged white light in ultrahigh vacuum (UHV) with a pressure of 1 × 10 −8 mbar . The UHV environment approximately corresponds to the geosynchronous orbit where the communication and meteorological satellites work.…”