Boosting Perovskite Solar Cells with New Self‑Assembled Layers

Scientists have long used a material called Me‑4PACz, or Me4, as a layer that pulls holes out of inverted perovskite solar cells. The layer is handy, but it often clumps together in solution and does not spread well over the next layer. Because of this, the contact between layers is weak and the crystal growth inside the cell is not perfect. The result is energy loss that hurts efficiency. To fix these problems, researchers designed two new molecules: LYS‑H and its fluorinated version LYS‑F. Both have a donor‑acceptor shape that makes the surface more polar, helping holes move out faster. They also carry special groups that protect the hidden interface where the perovskite sits. The molecules include a triphenylamine core that can stack against the carbazole parts of Me4 through π‑π interactions. This stacking stops Me4 from clumping and makes the whole self‑assembled layer smoother.The new molecules also improve how the liquid precursor wets the surface. A wetting surface lets the perovskite spread evenly, which in turn encourages better crystal growth. When LYS‑F is used, its extra fluorine atoms lower the energy level of the highest occupied molecular orbital. This change brings the molecule’s work function closer to that of the perovskite, aligning their energy levels more closely and cutting down on defects at the boundary. Devices that combine Me4 with LYS‑F show a power conversion efficiency of 25. 02 % and a fill factor of 83. 64 %. These numbers are higher than devices that use only Me4 or LYS‑H alone. Moreover, the new composites stay stable for longer periods when kept in dry air at room temperature, even without any protective covering. The study demonstrates that a thoughtful mix of chemical design and layer assembly can solve multiple issues at once. By improving hole extraction, surface wettability, and crystal quality, the new donor‑acceptor layers push perovskite solar cells closer to their theoretical limits.