Crystal Growth Regulation of Ruddlesden–Popper Perovskites via Self-Assembly of Semiconductor Spacers for Efficient Solar Cells

The crystal growth and orientation of two-dimensional (2D) perovskite films significantly impact solar cell performance. Here, we incorporated robust quadrupole-quadrupole interactions to govern the crystal growth of 2D Ruddlesden–Popper (RP) perovskites. This was achieved through the development of two unique semiconductor spacers, namely PTMA and 5FPTMA, with different dipole moments. The ((5FPTMA)_0.1(PTMA)_0.9)₂MA_n−1Pb_nI_3n+1 (nominal n=5, 5F/PTMA−Pb) film shows a preferred vertical orientation, reduced grain boundaries, and released residual strain compared to (PTMA)₂MA_n−1Pb_nI_3n+1 (nominal n=5, PTMA−Pb), resulting in a decreased exciton binding energy and reduced electron-phonon coupling coefficients. In contrast to PTMA−Pb device with an efficiency of 15.66 %, the 5F/PTMA−Pb device achieved a champion efficiency of 18.56 %, making it among the best efficiency for 2D RP perovskite solar cells employing an MA-based semiconductor spacer. This work offers significant insights into comprehending the crystal growth process of 2D RP perovskite films through the utilization of quadrupole-quadrupole interactions between semiconductor spacers.