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 H 3 N−C 4 H 6 (OH) 2 −NH 3 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.

We describe the unusual properties of γ-SnSe, a new orthorhombic binary phase in the tin monoselenide system. This phase exhibits an ultranarrow band gap under standard pressure and temperature conditions, leading to high conductivity under ambient conditions. Density functional calculations identified the similarity and difference between the new γ-SnSe phase and the conventional α-SnSe based on the electron localization function. Very good agreement was obtained for the band gap width between the band structure calculations and the experiment, and insight provided for the mechanism of reduction in the band gap. The unique properties of this material may render it useful for applications such as thermal imaging devices and solar cells.

A "single pot" solution deposition methodology was employed to fabricate phase controlled lead-doped tin monosulfide thin films. Different Pb2+:SnS2+ cation ratios were used for preparing SnS:Pb thin films on GaAs...