Metal Organic Frameworks as Molecular Encapsulants to prevent Efficiency Losses in Perovskite Solar Cells

Abstract

Perovskite solar cells (PSCs) exhibit exceptional power conversion efficiencies; however, their commercial deployment remains hindered by pronounced instability under environmental stressors such as moisture, oxygen, elevated temperatures, and ultraviolet (UV) radiation. In this work, we present the design and integration of mixed-matrix thermoplastic polyurethane (TPU) encapsulant films embedded with zeolitic imidazolate framework-8 (ZIF-8) and its fluorinated-silane–functionalized analogue (F-ZIF8). These films serve as intermediate barrier layers in the glass–glass encapsulation architecture of p–i–n structured PSCs employing a triple-cation perovskite composition (Cs₀.₀₃MA₀.₀₇FA₀.₉PbI₃). The incorporation of MOF nanofillers imparts a tortuous diffusion pathway that significantly impedes moisture ingress, while maintaining a low lamination temperature (~110 °C) compatible with the thermal sensitivity of the perovskite absorber layer. Under accelerated humidity aging conditions (relative humidity > 85 %, 25 °C), devices encapsulated with TPU/ZIF8 and TPU/F-ZIF8 retained 84 % and 81 %, respectively, of their initial power conversion efficiency (PCE) after 70 days. In contrast, devices encapsulated with pristine TPU exhibited a markedly shorter T₈₀ lifetime of only 25 days. These findings highlight the potential of MOF-based mixed-matrix TPU films as high-performance encapsulants, capable of enhancing the operational durability of PSCs under harsh environmental conditions. This approach represents a viable strategy toward the development of commercially relevant perovskite photovoltaic technologies with prolonged service lifetimes.