Structural and transport studies from air-stable hybrid perovskite thin films*

Traditionally, MAPbX₃ (X = Br, I, or Cl) hybrid organic-inorganic perovskite films have been deposited with spin coating techniques which cause degradation under ambient atmospheric conditions. We demonstrate the feasibility of stable MAPbI₃ thin films grown by a facile two-step low-pressure vapor deposition process in a single reactor. Absorption measurements confirm excellent stability after three weeks. In confluence with the absorption data, synchrotron x-ray diffraction experiments reveal good structural stability on the timescale of several months. Temperature dependent transport measurements show sharp inflection points of the resistance curve at distinct temperatures. One inflection point occurs precisely at the expected tetragonal to orthorhombic transition, however, another inflection deviates significantly from the expected tetragonal to cubic transition. Consequently, we conducted temperature dependent laboratory-based x-ray diffraction measurements that also suggest a transition below the commonly reported tetragonal/cubic transition temperature. Concerning device application, the MAPbI₃ films were incorporated into solar cells that maintained the majority of their efficiency and energy yield on the timescale of weeks.