Highly‐Oriented 3D Perovskite Films Synthesized by the Assisted Growth of Large‐Area 2D Perovskite Nanosheets With n = 1

Tandem solar cells combining crystalline silicon and perovskite have received extensive attention in recent years. One of the key challenges of this technique is the preparation of high‐quality perovskite films. In this paper, 3D perovskite films featuring ultra‐high crystallinity and a preferred orientation were synthesized, facilitated by the introduction of large‐area 2D perovskite nanosheets (n = 1) during preparation. The density of deep defects was dramatically reduced, shifting the dominant recombination mechanism from deep defects to shallow defects and resulting in a substantial suppression of non‐radiative recombination losses. The fabricated PSCs (E g = 1.697 eV) achieved a PCE of 21.36% with a hysteresis coefficient <1%, a stabilized power output (SPO) of 20.75%, and no significant decay after 300 s. Under storage aging conditions of 30% humidity and 25°C, T 90 ≈ 440 h was reached. Our research provides a new solution for the synthesis of highly ordered perovskite polycrystalline films.