Template-Assisted\nGrowth of High-Quality α‑Phase\nFAPbI<sub>3</sub> Crystals in Perovskite Solar Cells Using Thiol-Functionalized\nMoS<sub>2</sub> Nanosheets

Formamidinium\nlead iodide (FAPI) has gained attention for hybrid\nperovskite solar cell (PSC) applications due to its enhanced stability\nand narrow bandgap. However, a significant challenge remains in inducing\nand stabilizing the elusive perovskite “black phase”photoactive\ncubic α-FAPIas the relatively bulky FA<sup>+</sup> cations\ntend to favor the thermodynamically stable nonphotoactive “yellow\nphase”. In this study, we present a templated growth strategy\nemploying thiol-functionalized MoS<sub>2</sub> nanosheets as templates.\nBy introduction of 3-mercaptopropionic acid (MPA)-functionalized MoS<sub>2</sub> as a growth template, precise control over crystal formation\nwas achieved, favoring the growth of high-quality α-FAPI films.\nThese advanced templated films exhibited substantial improvements\nin charge transport properties, efficient light absorption, and enhanced\ncharge extraction. As a result, the PSCs achieved a significantly\nenhanced power conversion efficiency (PCE) compared to the nontemplated\ncontrol device, increasing from 20.6 to 22.5%. The MoS<sub>2</sub>-incorporated device also demonstrated excellent shelf stability,\nmaintaining 91% of the initial PCE even after 1600 h of storage without\ndevice encapsulation.