Optimization Charge-Carrier Properties of 2D Ruddlesden–Popper Perovskite for Solar Cells

Two-dimensional (2D) perovskites are tailored-photoelectric-responsive materials owing to their lattice softness and designable multifunctional spacer cations. However, the inferior charge-carrier characteristics in these 2D systems are intolerable for photovoltaic devices. Here, we introduced a novelty spacer cation 3,3-difluoropyrrolidinium (DFP) to synthesize 2D Ruddlesden–Popper (RP) perovskite, (DFP) 2 PbI 4 . The multiple hydrogen bonds in the spacing region of (DFP) 2 PbI 4 drive the structure toward uniqueness with the average Pb─I─Pb bond angles over 170°. This merit coupled with the large dipole moment of DFP demonstrates the unique bandgap (2.20 eV) and small exciton binding energies (99.76 meV) of (DFP) 2 PbI 4 . With the stacking of inorganic layers, the (DFP) 2 MA 4 Pb 5 I 16 (MA +: CH 3 NH 3 + ) film demonstrated an improved electron diffusion length (920 nm) and fast carrier extraction (0.73 μs) at the device level. The resultant (DFP) 2 MA 4 Pb 5 I 16 solar cells achieved a champion power conversion efficiency (PCE) of 19.43%. Furthermore, the unencapsulated devices exhibited excellent stability under continuous illumination and persistent heating conditions.