Efficient Slantwise Aligned Dion-Jacobson Phase Perovskite Solar Cells Based on Trans-1,4-Cyclohexanediamine

The crystalline orientation and phase distribution are two important parameters for high-performance 2D perovskite solar cells. Therefore, it is essential to understand how the structure of spacer ligands influences the orientation and phase distribution of resulting 2D perovskite films. In this work, a new member of Dion-Jacobson (DJ) phase 2D perovskites based on trans-1,4-cyclohexanediamine (CHDA) is demonstrated and it is found that the crystalline orientation is self-aligned spontaneously, which is different from the well-known graded distribution in controlled sample with its isomer 1,6-diaminohexane (HDA) as spacer ligand. Grazing incident X-ray scattering suggests that the exact alignment is strongly slantwise to the substrate while it is still beneficial for charge transfer along the vertical structure of devices. The devices can achieve high efficiency up to 15.01% for (CHDA)MA₃ Pb₄ I₁₃ (n = 4), one of the highest efficiencies reported by now. The encapsulated (CHDA)MA₃ Pb₄ I₁₃ (n = 4) devices can retain 80.7% efficiency for 270 min under continuous maximum power point tracking. (CHDA)MA₃ Pb₄ I₁₃ (n = 4) devices can retain 96.5% efficiency under 60 °C and 74.4% efficiency under 70 °C heating for 68 h. The results demonstrate the slantwise aligned DJ phase perovskite solar cells with excellent stability.