Significantly improved black phase stability of FAPbI₃ nanowires via spatially confined vapor phase growth in nanoporous templates

Abstract

The formamidinium lead iodide (FAPbI3) perovskite has attracted immense research interest as it has much improved stability than methylammonium lead iodide (MAPbI3) while still maintaining excellent optoelectronic properties. Compared to MAPbI3, FAPbI3 has shown an elevated decomposition temperature and a slower decomposition process and therefore it is considered as a more promising candidate for future high-efficiency and reliable optoelectronic devices. However, these excellent optoelectronic properties only exist in the alpha phase and this phase will spontaneously transform into an undesired delta phase with much poorer optoelectronic properties regardless of the environment. This is the main challenge for the application of the FAPbI3 perovskite. Herein, we report a novel strategy to stabilize the cubic black phase of FAPbI3 by using nanoengineering templates. Without further treatment, the black phase can be held over 7 months under ambient conditions and 8 days in an extreme environment with a Relative Humidity (RH) of 97%. A systematic study further reveals that this great improvement can be attributed to the spatial confinement in anodized alumina membrane (AAM) nanochannels, which prohibits the unwanted α-to-δ phase transition by restricting the expansion of NWs in the ab plane, and the excellent passivation against water molecule invasion. Meanwhile, we also demonstrate the potency of these NWs in practical applications by configuring them into photodetectors, which have shown reasonable response and excellent device stability.

A biomimetic eye with a hemispherical perovskite nanowire array retina

“…It can reach up to 303.2 mAW -1 , which is among the highest in the reported photoelectrochemical (PEC) photodetectors (Extended Data Table 1) to our best knowledge. And it is in par with that of solidstate photodetectors based on perovskite NW arrays reported earlier 7,8 . Under the lowest radiation level measured, the number of photons received per second by an individual nanowire can be estimated as 23 photons (Extended Data).…”

“…These components mimic biological eye lens, retina and nerve fibers behind the retina, respectively. Among them, the key component is the artificial retina made of a high-density array of NWs grown inside hemispherical porous-alumina-membrane (PAM) via a vapor-phase growth process [7][8][9] .…”

Enhancing High Humidity Stability of Quasi‐2D Perovskite Thin Films through Mixed Cation Doping and Solvent Engineering

“…Their larger cation radius decreases the optical band gap from 1.54 to 1.47 eV, broadening absorption into the near‐infrared with increased thermal stability . Tremendous efforts have been devoted to improve stability of FAPbI 3 perovskite solar cells, while maintaining excellent optoelectronic properties . However, the unwanted α‐to‐δ phase transition of hexagonal crystals at room temperature, surface morphology, and film uniformity across its thickness are major challenges .…”

Recent Progress on Interface Engineering for High‐Performance, Stable Perovskites Solar Cells

“…The long‐term stability of PSCs and their degradation mechanism is under intense investigation. [ 9 ] Researchers have witnessed the rapid degradation of 3D PVSK when it is exposed to moisture, oxygen, elevated temperature, and UV light. [ 10 ] The primary reason for the instability is the moisture‐induced degradation.…”