Hydroxyl Functional Groups in Two-Dimensional Dion–Jacobson Perovskite Solar Cells

In this work we demonstrate a new diammonium spacer molecule with hydroxyl functional groups forming a Dion–Jacobson perovskite. Polarization modulation infrared reflection absorption spectroscopy reveal hydrogen bonding between the iodide to the spacer molecule and in between the OH groups. As a result, we were able to demonstrate n = 5 low dimensional perovskite solar cell (LDPSC) with an efficiency of 10%. Photoconductivity measurements and scanning tunneling spectroscopy draw the band structure of this low dimensional perovskite (LDP) revealing in-gap states adjacent to the conduction band edge, consistent with Shockley–Reed–Hall modeling of the temperature-dependent photoconductivity. The LDPSC based on the diammonium spacer H3N–C4H6(OH)2–NH3 shows enhanced stability under a relative humidity of more than 50% over 1030 h. Evaluating the mechanism of the cell shows a misalignment of the hole selective contact with the LDP. Improving this interface can increase further the photovoltaic performance, demonstrating the potential of this new type of diammonium spacer in LDP.